Cross-linked fatty acid-based biomaterials

ABSTRACT

Fatty acid-derived biomaterials, methods of making the biomaterials, and methods of using them as drug delivery carriers are described. The fatty acid-derived biomaterials can be utilized alone or in combination with a medical device for the release and local delivery of one or more therapeutic agents. Methods of forming and tailoring the properties of said biomaterials and methods of using said biomaterials for treating injury in a mammal are also provided.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/104,568, filed Oct. 10, 2008. This application is also acontinuation-in-part of U.S. patent application Ser. No. 11/582,135,filed Oct. 16, 2006, which claims priority to U.S. Provisional PatentApplication Ser. No. 60/727,312, filed on Oct. 15, 2005. Thisapplication is also a continuation-in-part of U.S. patent applicationSer. No. 11/237,264, filed Sep. 28, 2005, which claims priority to U.S.Provisional Application No. 60/613,808, filed Sep. 28, 2004. Thisapplication is also a continuation-in-part of U.S. patent applicationSer. No. 11/236,908, filed Sep. 28, 2005, which claims priority to U.S.Provisional Application No. 60/613,745, filed Sep. 28, 2004. The entirecontents of these previously filed applications are hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION

Vascular interventions, such as vascular reperfusion procedures, balloonangioplasty, and mechanical stent deployment, can often result invascular injury following mechanical dilation and luminal expansion of anarrowed vessel. Often, subsequent to such intravascular procedures,neointimal proliferation and vascular injury remodeling occurs along theluminal surface of the injured blood vessel; more specifically,remodeling occurs in the heart, as well as in vulnerable peripheralblood vessels like the carotid artery, iliac artery, femoral andpopliteal arteries. No known mechanical suppression means have beenfound to prevent or effectively suppress such cellular proliferationfrom occurring immediately following vascular injury resulting frommechanical intervention and catheter directed reperfusion procedures.Left untreated, restenosis commonly occurs following a vascularintervention treated within the treated vessel lumen within weeks of avascular injury. Restenosis, induced by localized mechanical injurycauses proliferation of remodeled vascular lumen tissue, resulting inre-narrowing of the vessel lumen, which can lead to thrombotic closurefrom turbulent blood flow fibrin activation, platelet deposition andaccelerated vascular flow surface injury. Restenosis pre-disposes thepatient to a thrombotic occlusion and the stoppage of flow to otherlocations, resulting in critical ischemic events, often with morbidity.

Restenosis initiated by mechanical induced vascular injury cellularremodeling can be a gradual process. Multiple processes, includingfibrin activation, thrombin polymerization and platelet deposition,luminal thrombosis, inflammation, calcineurin activation, growth factorand cytokine release, cell proliferation, cell migration andextracellular matrix synthesis each contribute to the restenoticprocess. While the exact sequence of bio-mechanical mechanisms ofrestenosis are not completely understood, several suspected biochemicalpathways involved in cell inflammation, growth factor stimulation andfibrin and platelet deposition have been postulated. Cell derived growthfactors such as platelet derived growth factor, fibroblast growthfactor, epidermal growth factor, thrombin, etc., released fromplatelets, invading macrophages and/or leukocytes, or directly from thesmooth muscle cells, provoke proliferative and migratory responses inmedial smooth muscle cells. These cells undergo a change from thecontractile phenotype to a synthetic phenotype. Proliferation/migrationusually begins within one to two days post-injury and peaks several daysthereafter. In the normal arterial wall, smooth muscle cells proliferateat a low rate, approximately less than 0.1 percent per day.

However, daughter cells migrate to the intimal layer of arterial smoothmuscle and continue to proliferate and secrete significant amounts ofextracellular matrix proteins. Proliferation, migration andextracellular matrix synthesis continue until the damaged endotheliallayer is repaired, at which time proliferation slows within the intima,usually within seven to fourteen days post-injury. The newly formedtissue is called neointima. The further vascular narrowing that occursover the next three to six months is due primarily to negative orconstrictive remodeling.

Simultaneous with local proliferation and migration, inflammatory cellsderived from the medial layer of the vessel wall continually invade andproliferate at the site of vascular injury as part of the healingprocess. Within three to seven days post-injury, substantialinflammatory cell formation and migration have begun to accumulate alongthe vessel wall to obscure and heal over the site of the vascularinjury. In animal models, employing either balloon injury or stentimplantation, inflammatory cells may persist at the site of vascularinjury for at least thirty days. Inflammatory cells may contribute toboth the acute and protracted chronic phases of restenosis andthrombosis.

Today, a preferred approach to the local delivery of a drug to the siteof vascular injury caused by an intravascular medical device, such as acoronary stent, is to place a drug eluting coating on the device.Clinically, medical devices coated with a drug eluting coating comprisedof either a permanent polymer or degradable polymer and an appropriatetherapeutic agent have shown angiographic evidence that vascular wallproliferation following vascular injury and/or vascular reperfusionprocedures can be reduced, if not eliminated, for a certain period oftime subsequent to balloon angioplasty and/or mechanical stentdeployment. Local delivery of a single sirolimus or taxol compound via adrug eluting medical device has been shown to be effective at minimizingor preventing cellular proliferation and cellular remodeling whenapplied immediately after vascular injury. Various analogs of these twoanti-proliferative compound examples have also been shown experimentallyand clinically to exhibit similar anti-proliferative activity withsimilar drug eluting coatings. However, anti-proliferative compoundssuch as sirolimus and taxol, together with a polymeric drug elutingcoating have also been shown clinically to exhibit a number of toxicside effects, during and after principal drug release from the drugeluting coating. These chronic and or protracted side effects placelimits on the amount of drug that can actually be delivered over a givenperiod of time, as well as challenge the compatibility of the polymercoatings used to deliver a therapeutic agent locally to the site of thevascular injury when applied directly to a site of inflammation and orcellular remodeling. In addition, local overdosage of compounds likesirolimus and taxol can prevent, limit or even stop cellular remodelingor proliferation in and around the localized tissue area of the medicaldevice. For example, a lack of endothelial cell coverage during theinterruption of cell proliferation throughout the vascular injuryhealing process exhibits a high potential for luminal thrombosis wherebyfibrin and a constant deposition of platelets blanket the exposed andnon-healed medical device and/or damaged vascular injury. Withoutuninterrupted systemic support or administration of an anti-plateletmedication like clopidegrel combined with an anti-clotting agent, suchas ASA, prior to and following deployment of a drug eluting medicaldevice, such devices have been shown clinically to thrombose and occludewithin days of deployment. In addition, although these commerciallyavailable drug eluting polymer coatings employed on medical devices aregenerally characterized as being biocompatible, the lack of chemicalhydrolysis, degradation and absorption of these polymer-basedchemistries into smaller, easier to metabolize chemical components orproducts have been now been clinically demonstrated to initiate aprotracted localized inflammatory response at the site of the vascularinjury, which may lead to unexpected thromobotic occlusion within daysof stopping anti-platelet medication.

Wound healing or response to in-vivo injury (e.g., hernia repair)follows the same general biological cascade as in vascular injury (see,e.g., Y. C. Cheong et al. Human Reproduction Update. 2001; Vol. 7, No.6, pgs 556-566). This cascade includes inflammation of native tissuefollowed by migration and proliferation of cells to mitigate theinflammatory response, including platelets and macrophages, and asubsequent healing phase which includes fibrin deposition and theformation of fibrin matrix followed by tissue remodeling. In the case ofhernia repair, abnormal peritoneal healing can occur when there is theexpression of inflammatory cytokines from macrophages (e.g., α-TNF) thatcan result in an inability of the fibrin matrix to be properly brokendown and can result in the formation of adhesions (Y. C. Cheong et al.,2001). Abdominal adhesions formed after hernia repair can result inpain, bowel strangulation, infertility and in some cases death (Y. C.Cheong et al., 2001).

The sustained nature of the thrombotic and inflammatory response toinjury makes it desirable to provide a biomaterial that can reduce theincidence of inflammatory and foreign body responses after implantation.It would also be preferable to have a biomaterial that provides releaseof one or more therapeutic agents over a period of time in order tominimize such cell activated responses. Additionally, such a biomaterialwould also preferably be metabolized via a bioabsorption mechanism.

SUMMARY OF THE INVENTION

What is desired is a biomaterial (e.g., a coating or stand-alone film)that can be utilized alone or as a drug delivery carrier that preventsor diminishes chronic inflammation due to either the therapeutic agentor hydrolysis products of the coating. Furthermore, it is desirable thatthe biomaterial release and deliver therapeutic agents in a sustainedand controlled fashion to local tissue. The present invention isdirected toward various solutions that facilitate addressing this need.

What is also desired is a biomaterial (e.g., a coating or stand-alonefilm) that can be bioabsorbed by cells and that can deliver a drugwithout inducing chronic localized inflammation to tissues (e.g., theperitoneal or vascular tissue) that has been injured mechanically or byreperfusion injury, whereby the biomaterial (e.g., coating orstand-alone film) and the therapeutic agent are ingested and metabolizedby the cell, as it consumes the hydrolysis products of the biomaterialwith the drug.

In various aspects, the biomaterial is a coating for a medical device,or a stand-alone film. The biomaterial can be a hydrophobic, fattyacid-derived, cross-linked biomaterial (referred to herein as a “fattyacid-derived biomaterial”). In various embodiments, the fattyacid-derived biomaterial is non-polymeric. In certain instances, asdescribed herein, the source of the fatty acid is an oil, e.g., a fishoil. In such an instance, the fatty acid-derived biomaterial can also bereferred to as an “oil-derived biomaterial.”

In various aspects, the present invention may provide methods forproducing a hydrophobic, cross-linked fatty acid-derived biomaterial(e.g., a medical device coating or stand-alone film) that can beutilized alone or in combination with one or more therapeutic agents,wherein the therapeutic agents have a controlled loading and arereleased in a sustained manner as the coating is absorbed. In variousembodiments, provided are methods of tailoring the drug release profileof a hydrophobic, cross-linked fatty acid-derived biomaterial by controlof the process or preparation (e.g., curing) conditions used to producethe fatty acid-derived biomaterial (e.g., coating or stand-alone film)from a polyunsaturated fatty acid starting material, e.g., an oil, e.g.,a natural oil, containing starting material; the use of a free radicalscavenger in an oil containing starting material from which the fattyacid-derived biomaterial is formed, or combinations thereof. In variousembodiments, the methods of the present invention tailor the drugrelease properties of a fatty acid-derived biomaterial (e.g., coating orstand-alone film) by controlling the degree of cross-linking. In variousembodiments, the methods of the present invention tailor the drugdelivery properties of a fatty acid-derived biomaterial (e.g., coatingor stand-alone film) by controlling the level of fatty acids,tocopherols, lipid oxidation products, and soluble components in thecross-linked fatty acid-derived biomaterial.

In various aspects, the present invention may provide fatty acid-derivedbiomaterials (e.g., coating or stand-alone film) comprising one or moretherapeutic agents with a tailored release profile for one or more ofthe therapeutic agents. In various embodiments, the tailored releaseprofile comprises a sustained release profile. In various embodiments,the tailored release profile properties are controlled by the level offatty acids, tocopherols, lipid oxidation products, and solublecomponents in the fatty acid-derived biomaterial. In various aspects ofthe present invention, the fatty acid-derived biomaterial contains fattyacids, many of which originate as triglycerides. It has previously beendemonstrated that triglyceride byproducts, such as partially hydrolyzedtriglycerides and fatty acid molecules can integrate into cellularmembranes and enhance the solubility of drugs into cellular membranes(M. Cote, J. of Controlled Release. 2004, Vol. 97, pgs 269-281.; C. P.Burns et al., Cancer Research. 1979, Vol. 39, pgs 1726-1732; R. Beck etal., Circ. Res. 1998, Vol 83, pgs 923-931.; B. Henning et al.Arterioscler. Thromb. Vasc. Biol. 1984, Vol 4, pgs 489-797). Wholetriglycerides are known not to enhance cellular uptake as well as apartially hydrolyzed triglyceride, because it is difficult for wholetriglycerides to cross cell membranes due to their relatively largermolecular size. Vitamin E compounds can also integrate into cellularmembranes resulting in decreased membrane fluidity and cellular uptake(P. P. Constantinides. Pharmaceutical Research. 2006; Vol. 23, No. 2,243-255).

In various aspects, the present invention may provide a fattyacid-derived biomaterial (e.g., a medical device coating or stand-alonefilm) containing fatty acids, glycerides, lipid oxidation products andalpha-tocopherol in differing amounts and ratios to contribute to across-linked fatty acid-derived biomaterial in a manner that providescontrol over the cellular uptake characteristics of the cross-linkedfatty acid-derived biomaterial and any therapeutic agents mixed therein.

In various aspects, the present invention may provide coated medicaldevices having a fatty acid-derived biomaterial drug release coatingcomprising one or more layers of said fatty acid-derived biomaterial,wherein at least one of the fatty acid-derived biomaterial layerscontains one or more therapeutic agents. The coating can be ahydrophobic, fatty acid-derived, cross-linked biomaterial (derived,e.g., from fish oil). In various embodiments, the coating isnon-polymeric. In various embodiments, the drug release coatinghydrolyzes in vivo, into substantially non-inflammatory compounds. Invarious embodiments, the fatty acid-derived biomaterial is coated onto amedical device that is implantable in a patient to effect long termlocal delivery of the therapeutic agent to the patient. In variousembodiments the delivery is at least partially characterized by thetotal and relative amounts of the therapeutic agent released over time.In various embodiments, the tailored delivery profile is controlled bythe level of lipid oxidation and/or soluble components in the fattyacid-derived biomaterial. In various embodiments, the delivery profileis a function of the solubility and lipophilicity of the coatingcomponents and therapeutic agent in-vivo. The fatty acid-derivedbiomaterial can be a stand-alone film that has the properties discussedabove.

In various embodiments, the present invention may provide coatings wherethe drug release profile of the coating is tailored through theprovision of two or more coatings and selection of the location of thetherapeutic agent. The drug location can be altered, e.g., by coating abare portion of a medical device with a first starting material andcreating a first cured coating, then coating at least a portion of thefirst cured-coating with the drug-oil formulation to create a secondoverlayer coating. It is to be understood that the process of providingtwo layers can be extended to provide three or more layers, wherein atleast one of the layers comprises a fatty acid-derived biomaterial. Inaddition, one or more of the layers can be drug releasing, and the drugrelease profile of such layers can be tailored using the methodsdescribed herein.

In accordance with various embodiments of the present invention, thefatty acid-derived biomaterial (e.g., coating or stand-alone film)contains lipids. The fatty acid-derived biomaterial can be formed froman oil, such as fish oil, starting material. The fatty acid-derivedbiomaterial (e.g., coating or stand-alone film) can contain saturated,unsaturated, or polyunsaturated fatty acids. When the fatty acid-derivedbiomaterial is cross-linked, it can contain omega-3 fatty acids. Thefatty acid-derived biomaterial can also contain alpha-tocopherol orvitamin E.

The coatings can be formulated to contain a variety of other chemicalsand entities in addition to a therapeutic agent, including, but notlimited to, one or more of: a pharmaceutically acceptable carrier, anexcipient, a surfactant, a binding agent, an adjuvant agent, and/or astabilizing agent (including preservatives, buffers and antioxidants).In one embodiment, alpha-tocopherol TPGS may be added to the coatings ofthe present invention.

In various aspects, the present invention may provide methods fortreating injury in a mammal, such as, e.g., a human. In variousembodiments, the injury is a vascular injury. In various embodiments,the methods comprise locally administering one or more therapeuticagents in a therapeutically effective amount by sustained release of theone or more therapeutic agents from a coating comprising a fattyacid-derived biomaterial.

The teachings herein demonstrate that the cured coatings and stand-alonefilms provided herein provide the ability to regulate the releaseprofile of drug-loaded fatty acid-derived biomaterials from the films orfrom implantable devices. In various embodiments, the release profilecan be controlled through changes in oil chemistry by varying fattyacid-derived biomaterial (e.g., coating for a medical device orstand-alone film) composition and cure times. The teachings demonstratethat the release of therapeutic compounds from fatty acid-derivedbiomaterials (e.g., coating or stand-alone film) can be modified basedon altering the oil curing conditions, the oil starting material, lengthof curing, and amount of cross-linking. The teachings demonstrate thatthe cross-linking and gelation of the cured oil coatings and stand-alonefilm can be directly dependent on the formation of hydroperoxides in theoil component, which increases with increasing temperature and degree ofunsaturation of the oil. Dissolution experiments have shown that drugrelease is more rapid for the cross-linked coatings produced using lowertemperature curing conditions (e.g., around 150° F.) than highertemperature curing conditions (e.g., around 200° F.).

The teachings herein demonstrate that the use of vitamin E in cured oil(e.g., fish oil) coatings and stand-alone films is another method toalter the cross-linking and drug release properties of the coating.Vitamin E is an antioxidant that can slow down autoxidation in oil byreducing, it is believed, hydroperoxide formation during curing. Thiscan result in a decrease in the amount of cross-linking observed in acured oil coating or stand-alone film by inhibiting the formation ofadditional oxidative cross-linking species. Increasing the amount ofvitamin E in the coating or stand-alone film can result in lengtheningand slowing the release of a therapeutic agent from the coating. Forexample, the teachings herein demonstrate a lengthening and slowing ofthe release of Compound D from a hydrophobic, non-polymeric cross-linkedfatty acid-derived biomaterial coating into a dissolution buffer, due,it is believed, to Compound D's affinity for the fatty acid and vitaminE components in the cured fish oil coating. The teachings herein furtherindicate that vitamin E can also results in protecting a drug such asCompound D and increase the amount of such drug extracted from thecoating.

In one aspect, the present invention may provide a fatty acid-derivedbiomaterial (e.g., a medical device coating or stand-alone film) that isformed from a starting material comprising saturated, monounsaturated,and/or polyunsaturated fatty acids. In one aspect, the starting materialis an oil, e.g., a fish oil.

In another aspect, the invention may provide a coating for a medicaldevice comprising cross-linked fatty acids and glycerides. The source ofthe fatty acid can be an omega-3 fatty acid.

In another aspect, the invention may provide a coating for a medicaldevice comprising: a cross-linked fatty acid oil, comprisingapproximately 5-50% C₁₆ fatty acids, e.g., 5-30% C₁₆ fatty acids. In oneembodiment, the oil comprises 5-25% C₁₄ fatty acids. The oil can alsocomprise C₁₈ fatty acids (e.g., 0-60%), C₂₀ fatty acids (e.g., 0-40%),C₂₀ fatty acids (e.g., 0-40%), C₂₂ fatty acids (e.g., 0-30%), and/or C₂₄fatty acids (e.g., less than 5%).

In another aspect, the invention may provide a coating for a medicaldevice that hydrolyzes in vivo into fatty acids, glycerides andglycerol.

In still another aspect, the invention may provide a coating for amedical device comprising a non-polymeric, cross-linked fatty acid,comprising approximately 5-25% C₁₄ fatty acids and 5-50% C₁₆ fattyacids.

In yet another aspect, the invention may provide a coating for a medicaldevice comprising cross-linked fatty acids and glycerides, wherein thefatty acids and glycerides have disordered alkyl groups, which cause thebiomaterial to be flexible and hydratable.

In another aspect, the invention may provide a coating for a medicaldevice comprising a fatty acid-derived biomaterial wherein the fattyacid-derived biomaterial comprises delta-lactones.

In still another aspect, the invention may provide a coating for amedical device comprising lactone and ester cross links, as indicated byan infrared absorption spectrum having peaks at approximately 1740-1830cm⁻¹, respectively.

In yet another aspect, the invention may provide a coating for a medicaldevice comprising a cross-linked, oil-derived biomaterial, whereinapproximately 60-90% of the biomaterial is constituted by fatty acidswith molecular weights below 500.

In another aspect, the invention may provide a coating for a medicaldevice comprising an interesterified fatty acid. The fatty acid can bestearic acid, oleic acid, linoleic acid, alpha-linolenic acid, orgamma-linolenic acid. The source of the fatty acid can be an oil, e.g.,fish oil, olive oil, grape oil, palm oil, or flaxseed oil.

In yet another aspect, the invention may provide a coating for a medicaldevice comprising: a hydrophobic, non-polymeric cross-linked fatty acid;and a therapeutic agent; wherein the coating is sufficiently durable towithstand placement of the medical device in a patient.

In still another aspect, the invention may provide a coating for amedical device comprising an oil-derived biomaterial that has a contactangle of approximately 90-110 degrees when initially exposed to 0.1 MPBS solution, and, after approximately one hour of exposure, has acontact angle of 50-70 degrees.

In another aspect, the invention may provide a coating for a medicaldevice that inhibits production of α-TNF.

In another aspect, the invention may provide a fatty acid-derivedbiomaterial (e.g., a coating or stand-alone film) suitable for achievingmodulated healing in a tissue region in need thereof, wherein thebiomaterial is administered in an amount sufficient to achieve saidmodulated healing, wherein the modulated healing comprises a modulationof platelet or fibrin deposition in or near said tissue region. Thebiomaterial can contain monounsaturated and/or saturated fatty acids inthe coating. In one embodiment, the tissue region is the vasculature ofa subject.

In another aspect, the invention may provide a fatty acid-derivedbiomaterial (e.g., a coating or stand-alone film) suitable for achievingmodulated healing at a site of vascular injury in need thereof, whereinthe composition is administered in an amount sufficient to achieve saidmodulated healing, wherein the modulated healing comprises a modulationof at least one metric of organized tissue repair. In one embodiment,the vascular healing is the inflammatory stage of vascular healing. Inanother embodiment, the organized tissue repair comprises platelet orfibrin deposition at the site of vascular injury. In another embodiment,the modulation of at least one metric of organized tissue repair is adelay in the healing process at a site of vascular injury.

The modulated healing biomaterials described herein can be administeredto the tissue region in need thereof via a catheter, balloon, stent,surgical dressing or graft.

In one embodiment of the coating of the invention, the biomaterialcomprises lactone and ester cross-links.

In another embodiment of the coating of the invention, the biomaterialcontains disordered hydrocarbon chains as determined by infraredabsorption and X-ray diffraction.

In still another embodiment of the coating of the invention, thebiomaterial contains an amount of carboxylic acid groups sufficient tofacilitate hydrolysis in vivo. The coating can break down in vivo intonon-inflammatory components; or into fatty acids, glycerols, andglycerides.

In one embodiment of the coating of the invention, the biomaterial isconfigured to produce a glyceride upon metabolization in-vivo.

The coating of the invention may comprise approximately 30-90% saturatedfatty acids. In one embodiment, the coating comprises approximately30-80% unsaturated fatty acids. The coating can further comprise aglyceride. In another embodiment, said coating further comprises one ormore of the group consisting of a glyceride, a glycerol, and a fattyalcohol, any of which can be partially cross-linked. In anotherembodiment, the coating does not contain a cross-linking agent.

In one embodiment of the coating of the invention, the source of thefatty acids and glycerides is an oil, e.g., fish oil, olive oil, grapeoil, palm oil, or flaxseed oil. The oil can be alone or in combinationwith one or more oils. The coating can further comprise vitamin E. Thecoating can be associated with an implantable device, e.g., a medicaldevice, e.g., a catheter, a surgical mesh or a balloon.

The coating can further comprise a therapeutic agent, including, but notlimited to, an anti-proliferative drug, an anti-inflammatory agent, anantimicrobial agent or antibiotic agent. The therapeutic agent can beCompound A, Compound B, Compound C, Compound D, Compound E, or othercyclosporine derivatives or rapamycin derivatives.

The coating can have a release profile of the therapeutic agent in 0.01M phosphate buffered saline (PBS) out to about 5-20 days, e.g., about17-20 days, or more than 20 days. In another embodiment, the coatingreleases said therapeutic agent at a desired release rate in vivo.

In another aspect, the invention may provide a method of preparing acoating for a medical device, comprising heating a fatty acid-containing(e.g., polyunsaturated fatty acid-containing) oil in the presence ofoxygen, such that: the double bonds of the oil are oxidized; fatty acidsand glycerides are formed; and lactone and ester cross-links are formedbetween fatty acids and glycerides; such that the coating is formed. Inone embodiment of this method, the oil is continually heated, withoutinterruption.

In another aspect, the invention provides a method of preparing acoating for a medical device comprising heating a fatty acid-containing(e.g., polyunsaturated fatty acid-containing) oil in the presence ofoxygen, such that: the double bonds of the oil are oxidized; water,hydrocarbons and aldehydes are volatilized; and ester and lactonecross-links are formed; such that the coating is formed. In oneembodiment of this method, the oil is continually heated, withoutinterruption.

In either of the aforementioned methods, the oil can be heated atapproximately 140° F. to approximately 300° F., e.g., the oil is heatedat 150° F. or 200° F. The oil used in the methods can be fish oil. Themethods can also include the addition of a therapeutic agent. In aparticular embodiment, the time and temperature of the curing step isadjusted to tailor drug release. The therapeutic agent can be ananti-proliferative drug, an anti-inflammatory agent, an antimicrobialagent or antibiotic agent, such as Compound A, Compound B, Compound C,Compound D, Compound E, a cyclosporine derivative or a rapamycinderivative. The coatings produced by these methods can be combined withan organic solvent, and sprayed on a medical device, such as a stent, acatheter, a surgical mesh or a balloon. The coatings produced by thesemethods can comprise lactone and ester cross links, as indicated by aninfrared absorption spectrum having peaks at approximately 1740-1830cm⁻¹, respectively. The coatings can also contain disordered hydrocarbonchains with an infrared absorption at approximately 3000-2800 cm⁻¹.

In another a aspect, the invention may provide a method of forming afatty acid-derived biomaterial, comprising: continued heating of a fattyacid, thereby forming cross-links in the fatty acid; followed by thecleavage of C═C double bonds, which convert the fatty acids intooxidation byproducts. The oxidation byproducts can be aldehydes,ketones, alcohols, fatty acids, esters, lactones, ethers, orhydrocarbons. The byproducts can remain within the coating and/or arevolatilized during the heating process. The cross-links formed by thisprocess can be ester and lactone cross-links, wherein the ester andlactone cross-links occur via esterification, alcoholysis, acidolysis,or interesterification.

In another aspect, the invention may provide a method of forming a fattyacid-derived biomaterial, comprising: continued heating of a fatty acid,thereby oxidizing the double bonds of the unsaturated fatty acid chainswhile predominantly preserving triglyceride ester functional groups;thereby increasing the viscosity of the biomaterial. The ester linkagescan include ester, anhydride, aliphatic peroxide, and lactones. In oneembodiment, hydroxyl and carboxyl functional groups are formed from theoxidation process. In still another embodiment, oxidative byproducts ofEPA and DHA are formed.

In accordance with various embodiments of the methods provided herein,the curing (heating) steps occur without use of cross-linking agents.Also, curing time and temperature can be adjusted to tailor coatingdegradation. In another embodiment, vitamin E is added during theprocess to tailor the degree of cross-linking in the oil-derivedbiomaterial.

In one embodiment, the starting material used to prepare thebiomaterials (e.g., medical device coatings or stand-alone films) of theinvention is 40% (area % as determined by GC) polyunsaturated fattyacids.

In one embodiment, the fatty acid-derived biomaterial (e.g., coating orstand-alone film) of the invention has a fatty acid composition that issimilar to biological tissue.

In another aspect, the invention may provide a stand-alone film,comprising: a non-polymeric, cross-linked fatty acid, comprisingapproximately 5-50% C₁₆ fatty acids. The stand-alone film can alsocomprise 5-25% C₁₄ fatty acids. In another embodiment, the stand-alonefilm comprises 5-40%, e.g., 5-30%, C₁₆ fatty acids. The stand-alone filmcan also comprise vitamin E. The stand-alone film and coating may bebioabsorbable and it may maintain anti-adhesive properties. In anotherembodiment, the stand-alone film can further comprise a therapeuticagent, including, but not limited to, Compound A, Compound B, CompoundC, Compound D, Compound E, a cyclosporine derivative or rapamycinderivative. In one embodiment, the therapeutic agent is combined withthe fatty acid compound prior to formation of the film, resulting in thetherapeutic agent being interspersed throughout the film.

While many of the embodiments described above refer to a “coating” or“coating for a medical device,” it will be appreciated that the presentinvention can be implemented as a coating, as well as a stand-alonematerial, or other forms as described herein and, as would be understoodby those of ordinary skill in the art, having an outer surface and/orcoating that interacts with its environment upon implantation. Thus, theembodiments described herein, both those specifically referred to ascoatings and those referred to in other forms, to the extent they arebased on the fatty acid derived biomaterial as described herein, all areintended to fall within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects, embodiments, objects, features andadvantages of the invention can be more fully understood from thefollowing description in conjunction with the accompanying drawings. Inthe drawings, like reference characters generally refer to like featuresand structural elements throughout the various figures. The drawings arenot necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention.

FIG. 1 is a schematic illustration of an example of the creation ofperoxide and ether cross-linking in a polyunsaturated oil;

FIG. 2 is a schematic illustration of an example of the creation ofcarbon-carbon cross-linking in a polyunsaturated oil (Diels-Alder typereaction);

FIG. 3 shows the mechanism for the formation of the hydrophobic fattyacid-derived cross-linked biomaterial coating;

FIG. 4 shows a summary of fatty acid-derived biomaterial reactionchemistry;

FIG. 5 is a schematic of reactions of fatty acids that result in theformation of ester groups;

FIG. 6 schematically depicts the hydrolysis of the ester links in atriglyceride;

FIG. 7 shows bar graphs showing similarity of fatty acid compositionbetween a fatty acid-derived biomaterial coating and biological tissue;

FIG. 8 is a flow chart illustrating a method of making the coatedmedical device of the present invention, in accordance with oneembodiment of the present invention;

FIG. 9 is a flow chart illustrating a variation of the method of FIG. 8,in accordance with one embodiment of the present invention;

FIGS. 10A-10E are various images of coated medical devices;

FIG. 11 depicts an FTIR analysis of the final cured coating afterheating at 200° F. for 24 hr (Example 1);

FIGS. 12A-12B depict analysis of FTIR data discussed in Example 1;

FIG. 13 depicts the GC-FID fatty acid profile data discussed in Example1;

FIG. 14 depicts the GC-MS lipid oxidation byproduct analysis discussedin Example 1;

FIG. 15 depicts the FTIR analysis of different oil starting materialsafter curing into a fatty acid-derived biomaterial as described inExample 2;

FIG. 16 graphically depicts the differences in chemistry as determinedby FTIR analysis of different oil starting materials after curing into afatty acid-derived biomaterial as described in Example 2;

FIGS. 17A, 17B, 18A and 18B show the GC-FID fatty acid profile data ofdifferent oil starting materials before and after curing into a fattyacid-derived biomaterial as described in Example 2;

FIG. 19 illustrates the change in contact angle as a function ofhydration time for a fatty acid-derived biomaterial described in Example3;

FIGS. 20A and 20B depict the FTIR spectra of a fish-oil derivedbiomaterial as a function of hydration time for a fatty acid-derivedbiomaterial described in Example 3;

FIGS. 21A and 21B depict the FTIR spectra of a base-digested fish-oilderived biomaterial after neutralization as discussed in Example 4;

FIG. 22 provides the GC-FID fatty acid profile from a 0.1 M PBS solutionafter 30 day exposure of a fatty acid-derived biomaterial as describedin Example 5;

FIG. 23 depicts FTIR data discussed in Example 6;

FIG. 24 provides GC-FID fatty acid profile data from a fattyacid-derived biomaterial after explanation at various time points asdescribed in Example 7;

FIGS. 25 and 26 provide the characterization FTIR and GC-FID fatty acidprofile data for fatty acid-derived biomaterials produced usingdifferent methods of manufacture as described in Example 10.

FIGS. 27 and 28 depict drug release data in an aqueous media discussedin Example 11;

FIG. 29 depicts FTIR data for various vitamin E containing fattyacid-derived biomaterials as discussed in Example 11;

FIG. 30 depicts drug release data in an aqueous media discussed inExample 11;

FIG. 31 depicts a flow diagram presenting the process to create a curedcoating on a stent loaded with a therapeutic is outlined in Example 12;and

FIG. 32 shows the drug release profile for a cured oil therapeuticcoating in 0.01 M PBS buffer as described in Example 12.

DETAILED DESCRIPTION

A fatty acid-derived biomaterial can be utilized alone or in combinationwith a medical device optionally for the release and local delivery ofone or more therapeutic agents. Methods of forming and tailoring theproperties of said biomaterials and methods of using said biomaterialsfor treating injury in a mammal are also provided. Additionally, due tothe unique properties of the underlying chemistry of the biomaterial, itwill be demonstrated that the biomaterial (e.g., coating or stand-alonefilm) contains specific chemical components that assist in reducing aforeign body response and inflammation at the site of tissue injuryduring implantation that improves its in-vivo performance.

Prior to further describing embodiments of the invention, it may behelpful to generally and briefly describe injury and the biologicalresponse thereto.

Vascular Injury

Vascular injury causing intimal thickening can be broadly categorized asbeing either biologically or mechanically induced. Biologically mediatedvascular injury includes, but is not limited to, injury attributed toinfectious disorders including endotoxins and herpes viruses, such ascytomegalovirus; metabolic disorders, such as atherosclerosis; andvascular injury resulting from hypothermia, and irradiation.Mechanically mediated vascular injury includes, but is not limited to,vascular injury caused by catheterization procedures or vascularscraping procedures, such as percutaneous transluminal coronaryangioplasty; vascular surgery; transplantation surgery; laser treatment;and other invasive procedures which disrupt the integrity of thevascular intima or endothelium. Generally, neointima formation is ahealing response to a vascular injury.

Inflammatory Response

Wound healing upon vascular injury occurs in several stages. The firststage is the inflammatory phase. The inflammatory phase is characterizedby hemostasis and inflammation. Collagen exposed during wound formationactivates the clotting cascade (both the intrinsic and extrinsicpathways), initiating the inflammatory phase. After injury to tissueoccurs, the cell membranes, damaged from the wound formation, releasethromboxane A2 and prostaglandin 2-alpha, which are potentvasoconstrictors. This initial response helps to limit hemorrhage. Aftera short period, capillary vasodilatation occurs secondary to localhistamine release, and the cells of inflammation are able to migrate tothe wound bed. The timeline for cell migration in a normal wound healingprocess is predictable. Platelets, the first response cell, releasemultiple chemokines, including epidermal growth factor (EGF),fibronectin, fibrinogen, histamine, platelet-derived growth factor(PDGF), serotonin, and von Willebrand factor. These factors helpstabilize the wound through clot formation. These mediators act tocontrol bleeding and limit the extent of injury. Platelet degranulationalso activates the complement cascade, specifically C5a, which is apotent chemoattractant for neutrophils.

As the inflammatory phase continues, more immune response cells migrateto the wound. The second response cell to migrate to the wound, theneutrophil, is responsible for debris scavenging, complement-mediatedopsonization of bacteria, and bacteria destruction via oxidative burstmechanisms (i.e., superoxide and hydrogen peroxide formation). Theneutrophils kill bacteria and decontaminate the wound from foreigndebris.

The next cells present in the wound are the leukocytes and themacrophages (monocytes). The macrophage, referred to as theorchestrator, is essential for wound healing. Numerous enzymes andcytokines are secreted by the macrophage. These include collagenases,which debride the wound; interleukins and tumor necrosis factor (TNF),which stimulate fibroblasts (produce collagen) and promote angiogenesis;and transforming growth factor (TGF), which stimulates keratinocytes.This step marks the transition into the process of tissuereconstruction, i.e., the proliferative phase.

Cell Proliferation

The second stage of wound healing is the proliferative phase.Epithelialization, angiogenesis, granulation tissue formation, andcollagen deposition are the principal steps in this anabolic portion ofwound healing. Epithelialization occurs early in wound repair. At theedges of wounds, the epidermis immediately begins thickening. Marginalbasal cells begin to migrate across the wound along fibrin strandsstopping when they contact each other (contact inhibition). Within thefirst 48 hours after injury, the entire wound is epithelialized.Layering of epithelialization is re-established. The depths of the woundat this point contain inflammatory cells and fibrin strands. Agingeffects are important in wound healing as many, if not most, problemwounds occur in an older population. For example, cells from olderpatients are less likely to proliferate and have shorter life spans andcells from older patients are less responsive to cytokines.

Heart disease can be caused by a partial vascular occlusion of the bloodvessels that supply the heart, which is preceded by intimal smoothmuscle cell hyperplasia. The underlying cause of the intimal smoothmuscle cell hyperplasia is vascular smooth muscle injury and disruptionof the integrity of the endothelial lining. Intimal thickening followingarterial injury can be divided into three sequential steps: 1)initiation of smooth muscle cell proliferation following vascularinjury, 2) smooth muscle cell migration to the intima, and 3) furtherproliferation of smooth muscle cells in the intima with deposition ofmatrix. Investigations of the pathogenesis of intimal thickening haveshown that, following arterial injury, platelets, endothelial cells,macrophages and smooth muscle cells release paracrine and autocrinegrowth factors (such as platelet derived growth factor, epidermal growthfactor, insulin-like growth factor, and transforming growth factor) andcytokines that result in the smooth muscle cell proliferation andmigration. T-cells and macrophages also migrate into the neointima. Thiscascade of events is not limited to arterial injury, but also occursfollowing injury to veins and arterioles.

Granulomatous Inflammation

Chronic inflammation, or granulomatous inflammation, can cause furthercomplications during the healing of vascular injury. Granulomas areaggregates of particular types of chronic inflamatory cells which formnodules in the millimeter size range. Granulomas may be confluent,forming larger areas. Essential components of a granuloma arecollections of modified macrophages, termed epithelioid cells, usuallywith a surrounding zone of lymphocytes. Epithelioid cells are so namedby tradition because of their histological resemblance to epithelialcells, but are not in fact epithelial; they are derived from bloodmonocytes, like all macrophages. Epithelioid cells are less phagocyticthan other macrophages and appear to be modified for secretoryfunctions. The full extent of their functions is still unclear.Macrophages in granulomas are commonly further modified to formmultinucleate giant cells. These arise by fusion of epithelioidmacrophages without nuclear or cellular division forming huge singlecells which may contain dozens of nuclei. In some circumstances thenuclei are arranged round the periphery of the cell, termed aLanghans-type giant cell; in other circumstances the nuclei are randomlyscattered throughout the cytoplasm (i.e., the foreign body type of giantcell which is formed in response to the presence of other indigestibleforeign material in the tissue). Areas of granulomatous inflammationcommonly undergo necrosis.

Formation of granulomatous inflammation seems to require the presence ofindigestible foreign material (derived from bacteria or other sources)and/or a cell-mediated immune reaction against the injurious agent (typeIV hypersensitivity reaction).

Fatty Acid-Derived Biomaterials: Coatings and Stand-Alone Films

The fatty acid-derived biomaterials (e.g., coatings and stand-alonefilms) of the present invention comprise a hydrophobic cross-linkedfatty acid-derived biomaterial and optionally one or more therapeuticagents contained in the fatty acid-derived biomaterial. As used in thecontext of the cross-linked fatty acid-derived biomaterial coatingdescribed herein, the terms “soluble” and “insoluble” refer thesolubility of the coating in an organic solvent such as, e.g.,tetrahydrofuran (THF). In addition, the fatty acid-derived biomaterials(e.g., coatings and stand-alone films) of the present invention arebio-absorbable as described herein. The therapeutic agent can be anactive agent as contained in the coating and/or a prodrug that, e.g.,becomes active once released from the coating. In one embodiment of theinvention, the drug eluting fatty acid-derived biomaterial is across-linked fatty acid, e.g., an omega-3 fatty acid. The cross-linkedfatty acid can be non-polymeric. The source of the omega-3 fatty acidcan be a naturally occurring oil, e.g., a fish oil.

The hydrophobic fatty acid-derived biomaterial coatings and stand-alonefilms of the present invention can be formed from an oil component. Theoil component can be either an oil, or an oil composition. The oilcomponent can be a naturally occurring oil, such as fish oil, cod liveroil, flaxseed oil, grape seed oil, palm oil, or other oils havingdesired characteristics. The oil can also be a synthetic ornon-naturally occurring oil that contains fatty acids. One embodiment ofthe present invention makes use of a fish oil in part because of thehigh content of omega-3 fatty acids. The fish oil can also serve as ananti-adhesion agent. In addition, the fish oil maintainsanti-inflammatory or non-inflammatory properties as well. The presentinvention is not limited to formation of the fatty acid-derivedbiomaterials with fish oil as the oil starting material. However, thefollowing description makes reference to the use of fish oil as oneexample embodiment. Other oils can be utilized in accordance with thepresent invention as described herein.

It should be noted that as utilized herein, the term fish oil fatty acidincludes, but is not limited to, omega-3 fatty acid, oil fatty acid,free fatty acid, monoglycerides, di-glycerides, or triglycerides, estersof fatty acids, or a combination thereof. The fish oil fatty acidincludes one or more of arachidic acid, gadoleic acid, arachidonic acid,eicosapentaenoic acid, docosahexaenoic acid or derivatives, analogs andpharmaceutically acceptable salts thereof. Furthermore, as utilizedherein, the term free fatty acid includes but is not limited to one ormore of butyric acid, caproic acid, caprylic acid, capric acid, lauricacid, myristic acid, palmitic acid, palmitoleic acid, stearic acid,oleic acid, vaccenic acid, linoleic acid, alpha-linolenic acid,gamma-linolenic acid, behenic acid, erucic acid, lignoceric acid,analogs and pharmaceutically acceptable salts thereof. The oils,including fish oil, are cured as described herein to form a hydrophobiccross-linked fatty acid-derived biomaterial.

Some embodiments of the present invention may relate to bio-absorbablemedical device coatings and stand-alone films that can exhibitanti-inflammatory properties, non-inflammatory properties, andanti-adhesion properties, and the corresponding method of making. Thestand-alone film is generally formed of an oil, such as a fish oil. Inaddition, the oil composition can include a therapeutic agent component,such as a drug or other bioactive agent. The stand-alone film isimplantable in a patient for short term or long term applications. Asimplemented herein, the stand-alone film can be a non-polymericcross-linked fatty acid-derived biomaterial derived at least in partfrom a fatty acid compound, wherein the stand-alone film is prepared inaccordance with the methods of the invention. In accordance with furtheraspects of the present invention, the stand-alone film can furtherinclude a vitamin E compound forming a portion of the fatty acidcompound.

In accordance with further aspects of the present invention, thestand-alone film further includes a therapeutic agent. The therapeuticagent can include an agent selected from the group consisting ofantioxidants, anti-inflammatory agents, anti-coagulant agents, drugs toalter lipid metabolism, anti-proliferatives, anti-neoplastics, tissuegrowth stimulants, functional protein/factor delivery agents,anti-infective agents, imaging agents, anesthetic agents,chemotherapeutic agents, tissue absorption enhancers, anti-adhesionagents, germicides, analgesics, prodrugs, and antiseptics.

In accordance with further aspects of the present invention, thetherapeutic agent is combined with the fatty acid compound prior toformation of the film, resulting in the therapeutic agent beinginterspersed throughout the film. Alternatively, the therapeutic agentis applied to the film in the form of a coating. In accordance withfurther aspects of the present invention, the stand-alone film isbioabsorbable. The stand-alone film can further maintain anti-adhesiveproperties.

In accordance with still another embodiment of the present invention, amethod of forming a stand-alone film is introduced. The method includesproviding a fatty acid compound in liquid form and applying the fattyacid compound to a substrate. The method also includes curing the fattyacid compound to form the stand-alone film. In accordance with oneaspect of the present invention, the substrate includes expandedpolytetrafluoroethylene (ePTFE) or polytetrafluoroethylene (PTFE). Inaccordance with further aspects of the present invention, the curingincludes using at least one curing method selected from a group ofcuring methods including application of UV light and application ofheat. The UV light can also be applied to set the fatty acid compound byforming a skin on the top surface of the fatty acid compound in liquidform prior to additional curing. In accordance with further aspects ofthe present invention, the substrate has an indentation that is used asa mold to shape the stand-alone film. Alternatively, the method canfurther include the step of cutting the film to a desirable shape.

The stand-alone film of the present invention may be used as a barrierto keep tissues separated to avoid adhesion. Application examples foradhesion prevention include abdominal surgeries, spinal repair,orthopedic surgeries, tendon and ligament repairs, gynecological andpelvic surgeries, and nerve repair applications. The stand-alone filmmay be applied over the trauma site or wrapped around the tissue ororgan to limit adhesion formation. The addition of therapeutic agents tothe stand-alone films used in these adhesion prevention applications canbe utilized for additional beneficial effects, such as pain relief orinfection minimization. Other surgical applications of the stand-alonefilm may include using a stand-alone film as a dura patch, buttressingmaterial, internal wound care (such as a graft anastomotic site), andinternal drug delivery system. The stand-alone film may also be used inapplications in transdermal, wound healing, and non-surgical fields. Thestand-alone film may be used in external wound care, such as a treatmentfor burns or skin ulcers. The stand-alone film may be used without anytherapeutic agent as a clean, non-permeable, non-adhesive,non-inflammatory, anti-inflammatory dressing, or the stand-alone filmmay be used with one or more therapeutic agents for additionalbeneficial effects. The stand-alone film may also be used as atransdermal drug delivery patch when the stand-alone film is loaded orcoated with one or more therapeutic agents.

Oils

With regard to the aforementioned oils, it is generally known that thegreater the degree of unsaturation in the fatty acids the lower themelting point of a fat, and the longer the hydrocarbon chain the higherthe melting point of the fat. An unsaturated fat, thus, has a lowermelting point, and a saturated fat has a higher melting point. Thosefats having a lower melting point are more often oils at roomtemperature. Those fats having a higher melting point are more oftenwaxes or solids at room temperature. Therefore, a fat having thephysical state of a liquid at room temperature is an oil. In general,unsaturated fats are liquid oils at room temperature, and saturated fatsare waxes or solids at room temperature.

Polyunsaturated fats are one of four basic types of fat derived by thebody from food. The other fats include saturated fat, as well asmonounsaturated fat and cholesterol. Unsaturated fats can be furthercomposed of omega-3 fatty acids and omega-6 fatty acids. Under theconvention of naming the unsaturated fatty acid according to theposition of its first double bond of carbons, those fatty acids havingtheir first double bond at the third carbon atom from the methyl end ofthe molecule are referred to as omega-3 fatty acids. Likewise, a firstdouble bond at the sixth carbon atom is called an omega-6 fatty acid.There can be both monounsaturated and polyunsaturated omega fatty acids.

Omega-3 and omega-6 fatty acids are also known as essential fatty acidsbecause they are important for maintaining good health, despite the factthat the human body cannot make them on its own. As such, omega-3 andomega-6 fatty acids must be obtained from external sources, such asfood. Omega-3 fatty acids can be further characterized as containingeicosapentaenoic acid (EPA), docosahexanoic acid (DHA), andalpha-linolenic acid (ALA). Both EPA and DHA are known to haveanti-inflammatory effects and wound healing effects within the humanbody.

As utilized herein, the term “bio-absorbable” generally refers to havingthe property or characteristic of being able to penetrate the tissue ofa patient's body. In certain embodiments of the present inventionbio-absorption occurs through a lipophilic mechanism. The bio-absorbablesubstance can be soluble in the phospholipid bi-layer of cells of bodytissue, and therefore impact how the bio-absorbable substance penetratesinto the cells.

It should be noted that a bio-absorbable substance is different from abiodegradable substance. Biodegradable is generally defined as capableof being decomposed by biological agents, or capable of being brokendown by microorganisms or biological processes. Biodegradable substancescan cause inflammatory response due to either the parent substance orthose formed during breakdown, and they may or may not be absorbed bytissues.

Drug Delivery

The fatty acid-derived biomaterials (e.g, coatings and stand-alonefilms) may deliver one or more therapeutic agents locally to a targetedarea using a stand-alone film, medical device or apparatus bearing thecoating at a selected targeted tissue location of the patient thatrequires treatment. The therapeutic agent is released from the coatingto the targeted tissue location. The local delivery of a therapeuticagent enables a more concentrated and higher quantity of therapeuticagent to be delivered directly at the targeted tissue location, withouthaving broader systemic side effects. With local delivery, thetherapeutic agent that escapes the targeted tissue location dilutes asit travels to the remainder of the patient's body, substantiallyreducing or eliminating systemic side effects.

Targeted local therapeutic agent delivery using a fatty acid-derivedbiomaterial (e.g, coatings and stand-alone films) can be further brokeninto two categories, namely, short term and long term. The short termdelivery of a therapeutic agent occurs generally within a matter ofseconds or minutes to a few days or weeks. The long term delivery of atherapeutic agent occurs generally within weeks to months.

The phrase “sustained release” as used herein generally refers to therelease of a biologically active agent that results in the long termdelivery of the active agent.

The phrase “controlled release” as used herein generally refers to therelease of a biologically active agent in a substantially predictablemanner over the time period of weeks or months, as desired andpredetermined upon formation of the biologically active agent on themedical device from which it is being released. Controlled releaseincludes the provision of an initial burst of release upon implantation,followed by the substantially predictable release over theaforementioned time period.

Drug Release Mechanisms

Prior attempts to create films and drug delivery platforms, such as inthe field of stents, primarily make use of high molecular weightsynthetic polymer based materials to provide the ability to bettercontrol the release of the therapeutic agent. Essentially, the polymerin the platform releases the drug or agent at a predetermined rate onceimplanted at a location within the patient. Regardless of how much ofthe therapeutic agent would be most beneficial to the damaged tissue,the polymer releases the therapeutic agent based on properties of thepolymer, e.g., erosion of the polymeric material or diffusion of theagent through the polymer. Accordingly, the effect of the therapeuticagent is substantially local at the surface of the tissue making contactwith the medical device having the coating. In some instances the effectof the therapeutic agent is further localized to the specific locationsof, for example, stent struts or mesh pressed against the tissuelocation being treated. These prior approaches can create the potentialfor a localized toxic effect.

In various embodiments of the present invention, the fatty acid-derivedbiomaterial of the invention (e.g., coatings and stand-alone films)release one or more therapeutic agents by a dissolution mechanism, e.g.,dissolution of a therapeutic agent contained in a soluble component ofthe coating into the medium in contact with the coating, e.g., tissue.As a result, the drug release mechanism can be based on the solubilityof the therapeutic agent in the surrounding medium. For example, atherapeutic agent near the interface between the hydrophobic coating andthe surrounding medium can experience a chemical potential gradient thatcan motivate the therapeutic agent out of the oil based coating and intothe surrounding medium. Accordingly, in various embodiments, the releaseof a therapeutic agent is not rate-limited by diffusion or thehydrolysis of the coating.

In various embodiments, the break-down products of the fattyacid-derived biomaterial of the invention, e.g., a hydrophobic,cross-linked fatty acid-derived biomaterial, break-down intonon-inflammatory byproducts, e.g., free fatty acids and glycerides, thatthemselves can release one or more of the therapeutic agents via adissolution mechanism.

Therapeutic Agents

As utilized herein, the phrase “therapeutic agent(s)” refers to a numberof different drugs or agents available, as well as future agents thatmay be beneficial for use with the fatty acid-derived biomaterials(e.g., coatings and stand-alone films) of the present invention. Thetherapeutic agent component can take a number of different formsincluding anti-oxidants, anti-inflammatory agents, anti-coagulantagents, drugs to alter lipid metabolism, anti-proliferatives,anti-neoplastics, tissue growth stimulants, functional protein/factordelivery agents, anti-infective agents, anti-imaging agents, anestheticagents, therapeutic agents, tissue absorption enhancers, anti-adhesionagents, germicides, anti-septics, analgesics, prodrugs thereof, and anyadditional desired therapeutic agents such as those listed in Table 1below.

TABLE 1 CLASS EXAMPLES Antioxidants Alpha-tocopherol, lazaroid,probucol, phenolic antioxidant, resveretrol, AGI-1067, vitamin EAntihypertensive Diltiazem, nifedipine, verapamil AgentsAntiinflammatory Glucocorticoids (e.g. dexamethazone, Agentsmethylprednisolone), leflunomide, NSAIDS, ibuprofen, acetaminophen,hydrocortizone acetate, hydrocortizone sodium phosphate,macrophage-targeted bisphosphonates Growth Factor Angiopeptin, trapidil,suramin Antagonists Antiplatelet Agents Aspirin, dipyridamole,ticlopidine, clopidogrel, GP IIb/IIIa inhibitors, abcximab AnticoagulantBivalirudin, heparin (low molecular weight and Agents unfractionated),wafarin, hirudin, enoxaparin, citrate Thrombolytic Agents Alteplase,reteplase, streptase, urokinase, TPA, citrate Drugs to Alter LipidFluvastatin, colestipol, lovastatin, atorvastatin, Metabolism amlopidine(e.g. statins) ACE Inhibitors Elanapril, fosinopril, cilazaprilAntihypertensive Prazosin, doxazosin Agents AntiproliferativesCyclosporine, cochicine, mitomycin C, sirolimus and Antineoplasticsmicophenonolic acid, rapamycin, everolimus, tacrolimus, paclitaxel,QP-2, actinomycin, estradiols, dexamethasone, methatrexate, cilostazol,prednisone, cyclosporine, doxonibicin, ranpirnas, troglitzon, valsarten,pemirolast, C- MYC antisense, angiopeptin, vincristine, PCNA ribozyme,2-chloro-deoxyadenosine, mTOR targeting compounds Tissue growth Bonemorphogeneic protein, fibroblast growth stimulants factor Promotion ofhollow Alcohol, surgical sealant polymers, polyvinyl organ occlusion orparticles, 2-octyl cyanoacrylate, hydrogels, thrombosis collagen,liposomes Functional Protein/ Insulin, human growth hormone, estradiols,nitric Factor delivery oxide, endothelial progenitor cell antibodiesSecond messenger Protein kinase inhibitors targeting AngiogenicAngiopoetin, VEGF Anti-Angiogenic Endo statin Inhibitation of ProteinHalofuginone, prolyl hydroxylase inhibitors, C- Synthesis/ECM proteinaseinhibitors formation Antiinfective Agents Penicillin, gentamycin,adriamycin, cefazolin, amikacin, ceftazidime, tobramycin, levofloxacin,silver, copper, hydroxyapatite, vancomycin, ciprofloxacin, rifampin,mupirocin, RIP, kanamycin, brominated furonone, algae byproducts,bacitracin, oxacillin, nafcillin, floxacillin, clindamycin, cephradin,neomycin, methicillin, oxytetracycline hydrochloride, Selenium. GeneDelivery Genes for nitric oxide synthase, human growth hormone,antisense oligonucleotides Local Tissue Alcohol, H2O, saline, fish oils,vegetable oils, perfusion liposomes Nitric oxide Donor NCX 4016 - nitricoxide donor derivative of Derivatives aspirin, SNAP Gases Nitric oxide,compound solutions Imaging Agents Halogenated xanthenes, diatrizoatemeglumine, diatrizoate sodium Anesthetic Agents Lidocaine, benzocaineDescaling Agents Nitric acid, acetic acid, hypochlorite Anti-FibroticAgents Interferon gamma - 1b, Interluekin - 10 Immunosuppressive/Cyclosporine, rapamycin, mycophenolate Immunomodulatory motefil,leflunomide, tacrolimus, tranilast, Agents interferon gamma-1b,mizoribine, mTOR targeting compounds Chemotherapeutic Doxorubicin,paclitaxel, tacrolimus, sirolimus, Agents fludarabine, ranpirnase TissueAbsorption Fish oil, squid oil, omega 3 fatty acids, vegetable Enhancersoils, lipophilic and hydrophilic solutions suitable for enhancingmedication tissue absorption, distribution and permeation Anti-AdhesionHyaluronic acid, human plasma derived surgical Agents sealants, andagents comprised of hyaluronate and carboxymethylcellulose that arecombined with dimethylaminopropyl, ehtylcarbodimide, hydrochloride, PLA,PLGA Ribonucleases Ranpirnase Germicides Betadine, iodine, slivernitrate, furan derivatives, nitrofurazone, benzalkonium chloride,benzoic acid, salicylic acid, hypochlorites, peroxides, thiosulfates,salicylanilide Antiseptics Selenium Analgesics Bupivicaine, naproxen,ibuprofen, acetylsalicylic acid

Some specific examples of therapeutic agents useful in theanti-restenosis realm include cerivastatin, cilostazol, fluvastatin,lovastatin, paclitaxel, pravastatin, rapamycin, a rapamycin carbohydratederivative (for example, as described in US Patent ApplicationPublication 2004/0235762), a rapamycin derivative (for example, asdescribed in U.S. Pat. No. 6,200,985), everolimus, seco-rapamycin,seco-everolimus, and simvastatin. With systemic administration, thetherapeutic agent is administered orally or intravenously to besystemically processed by the patient. However, there are drawbacks to asystemic delivery of a therapeutic agent, one of which is that thetherapeutic agent travels to all portions of the patient's body and canhave undesired effects at areas not targeted for treatment by thetherapeutic agent. Furthermore, large doses of the therapeutic agentonly amplify the undesired effects at non-target areas. As a result, theamount of therapeutic agent that results in application to a specifictargeted location in a patient may have to be reduced when administeredsystemically to reduce complications from toxicity resulting from ahigher dosage of the therapeutic agent.

The term “mTOR targeting compound” refers to any compound whichmodulates mTOR directly or indirectly. An example of an “mTOR targetingcompound” is a compound that binds to FKBP 12 to form, e.g., a complex,which in turn inhibits phosphoinostide (PI)-3 kinase, that is, mTOR. Invarious embodiments, mTOR targeting compounds inhibit mTOR. SuitablemTOR targeting compounds include, for example, rapamycin and itsderivatives, analogs, prodrugs, esters and pharmaceutically acceptablesalts.

Calcineurin is a serine/threonine phospho-protein phosphatase and iscomposed of a catalytic (calcineurin A) and regulatory (calcineurin B)subunit (about 60 and about 18 kDa, respectively). In mammals, threedistinct genes (A-alpha, A-beta, A-gamma) for the catalytic subunit havebeen characterized, each of which can undergo alternative splicing toyield additional variants. Although mRNA for all three genes appears tobe expressed in most tissues, two isoforms (A-alpha and A-beta) are mostpredominant in brain.

The calcineurin signaling pathway is involved in immune response as wellas apoptosis induction by glutamate excitotoxicity in neuronal cells.Low enzymatic levels of calcineurin have been associated with Alzheimersdisease. In the heart or in the brain calcineurin also plays a key rolein the stress response after hypoxia or ischemia.

Substances which are able to block the calcineurin signal pathway can besuitable therapeutic agents for the present invention. Examples of suchtherapeutic agents include, but are not limited to, FK506, tacrolimus,cyclosporin and include derivatives, analogs, esters, prodrugs,pharmaceutically acceptably salts thereof, and conjugates thereof whichhave or whose metabolic products have the same mechanism of action.Further examples of cyclosporin derivatives include, but are not limitedto, naturally occurring and non-natural cyclosporins prepared by total-or semi-synthetic means or by the application of modified culturetechniques. The class comprising cyclosporins includes, for example, thenaturally occurring Cyclosporins A through Z, as well as variousnon-natural cyclosporin derivatives, artificial or synthetic cyclosporinderivatives. Artificial or synthetic cyclosporins can includedihydrocyclosporins, derivatized cyclosporins, and cyclosporins in whichvariant amino acids are incorporated at specific positions within thepeptide sequence, for example, dihydro-cyclosporin D.

In various embodiments, the therapeutic agent comprises one or more of amTOR targeting compound and a calcineurin inhibitor. In variousembodiments, the mTOR targeting compound is Compound D or a derivative,analog, ester, prodrug, pharmaceutically acceptably salts thereof, orconjugate thereof which has or whose metabolic products have the samemechanism of action. In various embodiments, the calcineurin inhibitoris a compound of Tacrolimus, or a derivative, analog, ester, prodrug,pharmaceutically acceptably salts thereof, or conjugate thereof whichhas or whose metabolic products have the same mechanism of action or acompound of Cyclosporin or a derivative, analog, ester, prodrug,pharmaceutically acceptably salts thereof, or conjugate thereof whichhas or whose metabolic products have the same mechanism of action.

The therapeutic agents that can be used with the fatty acid-derived,pre-cured biomaterials of the invention can also include antimicrobialagents, including, antivirals, antibiotics, antifungals andantiparasitics. Specific antimicrobial agents that can be used with thefatty acid-derived, pre-cured biomaterials of the invention includePenicillin G, ephalothin, Ampicillin, Amoxicillin, Augmentin, Aztreonam,Imipenem, Streptomycin, Gentamicin, Vancomycin, Clindamycin,Erythromycin, Azithromycin, Polymyxin, Bacitracin, Amphotericin,Nystatin, Rifampicin, Tetracycline, Doxycycline, Chloramphenicol,Nalidixic acid, Ciprofloxacin, Sulfanilamide, Gantrisin, Trimethoprim,Isoniazid (INH), para-aminosalicylic acid (PAS), and Gentamicin.

Therapeutically Effective Amounts and Dosage Levels

A therapeutically effective amount refers to that amount of a compoundsufficient to result in amelioration of symptoms, e.g., treatment,healing, prevention or amelioration of the relevant medical condition,or an increase in rate of treatment, healing, prevention or ameliorationof such conditions. When applied to an individual active ingredient,administered alone, a therapeutically effective amount refers to thatingredient alone. When applied to a combination, a therapeuticallyeffective amount can refer to combined amounts of the active ingredientsthat result in the therapeutic effect, whether administered incombination, serially or simultaneously. In various embodiments, whereformulations comprise two or more therapeutic agents, such formulationscan be described as a therapeutically effective amount of compound A forindication A and a therapeutically effective amount of compound B forindication B, such descriptions refer to amounts of A that have atherapeutic effect for indication A, but not necessarily indication B,and amounts of B that have a therapeutic effect for indication B, butnot necessarily indication A.

Actual dosage levels of the active ingredients in a fatty acid-derivedbiomaterial (e.g., coating and stand-alone film) of the presentinvention may be varied so as to obtain an amount of the activeingredients which is effective to achieve the desired therapeuticresponse without being unacceptably toxic. The selected dosage levelwill depend upon a variety of pharmacokinetic factors including theactivity of the particular therapeutic agent (drug) employed, or theester, salt or amide thereof, the mechanism of drug action, the time ofadministration, the drug release profile of the coating, the rate ofexcretion of the particular compounds being employed, the duration ofthe treatment, other drugs, compounds and/or materials used incombination with the particular compounds employed, and like factorsknown in the medical arts.

Other Agents

The fatty acid-derived biomaterials (e.g., coatings and stand-alonefilms) of the present invention can also comprise one or more otherchemicals and entities in addition to the therapeutic agent, including,but not limited to, one or more of: a pharmaceutically acceptablecarrier, an excipient, a surfactant, a binding agent, an adjuvant agent,and/or a stabilizing agent (including preservatives, buffers andantioxidants). The other agents can perform one or more functions, suchas, e.g., an adjuvant may also serve as a stabilizing agent.

In various embodiments, the coatings and stand-alone films of thepresent invention include one or more of a free radical scavenger anduptake enhancer. In various embodiments, the coatings and stand-alonefilms comprise vitamin E.

It should be noted that as utilized herein to describe the presentinvention, the term vitamin E and the term alpha-tocopherol, areintended to refer to the same or substantially similar substance, suchthat they are interchangeable and the use of one includes an implicitreference to both. Further included in association with the term vitaminE are such variations including but not limited to one or more ofalpha-tocopherol, beta-tocopherol, delta-tocopherol, gamma-tocopherol,alpha-tocotrienol, beta-tocotrienol, delta-tocotrienol,gamma-tocotrienol, alpha-tocopherol acetate, beta-tocopherol acetate,gamma-tocopherol acetate, delta-tocopherol acetate, alpha-tocotrienolacetate, beta-tocotrienol acetate, delta-tocotrienol acetate,gamma-tocotrienol acetate, alpha-tocopherol succinate, beta-tocopherolsuccinate, gamma-tocopherol succinate, delta-tocopherol succinate,alpha-tocotrienol succinate, beta-tocotrienol succinate,delta-tocotrienol succinate, gamma-tocotrienol succinate, mixedtocopherols, vitamin E TPGS, derivatives, analogs and pharmaceuticallyacceptable salts thereof.

Compounds that move too rapidly through a tissue may not be effective inproviding a sufficiently concentrated dose in a region of interest.Conversely, compounds that do not migrate in a tissue may never reachthe region of interest. Cellular uptake enhancers such as fatty acidsand cellular uptake inhibitors such as alpha-tocopherol can be usedalone or in combination to provide an effective transport of a givencompound to a given region or location. Both fatty acids andalpha-tocopherol can be included in the fatty acid-derived biomaterials(e.g., coatings and stand-alone films) of the present inventiondescribed herein. Accordingly, fatty acids and alpha-tocopherol can becombined in differing amounts and ratios to contribute to a fattyacid-derived biomaterial (e.g., coating and stand-alone film) in amanner that provides control over the cellular uptake characteristics ofthe coating and any therapeutic agents mixed therein.

For example, the amount of alpha-tocopherol can be varied in thecoating. Alpha-tocopherol is known to slow autoxidation in fish oil byreducing hydroperoxide formation, which results in a decrease in theamount of cross-linking in a cured fatty acid-derived biomaterial. Inaddition, alpha-tocopherol can be used to increase solubility of drugsin the oil forming the coating. In various embodiments, alpha-tocopherolcan protect the therapeutic drug during curing, which increases theresulting drug load in the coating after curing. Furthermore, withcertain therapeutic drugs, the increase of alpha-tocopherol in thecoating can serve to slow and extend drug release due to the increasedsolubility of the drug in the alpha-tocopherol component of the coating.

Curing and the Formation of Fatty Acid-Derived Biomaterials

Several methods are available to cure the oil starting materialcontaining one or more therapeutic agents to produce a fattyacid-derived biomaterial for a drug release and delivery coating orstand-alone film in accordance with the present invention (for example,as described in US Patent Application Publications 2008/0118550,2007/0202149, 2007/0071798, 2006/0110457, 2006/0078586, 2006/0067983,2006/0067976, 2006/0067975, which are incorporated herein by reference).Preferred methods for curing the starting material to produce a fattyacid-derived biomaterial of the present invention include, but are notlimited to, heating (e.g., employing an oven, a broadband infrared (IR)light source, a coherent IR light source (e.g., laser), and combinationsthereof) and ultraviolet (UV) irradiation. The starting material may becross-linked through auto-oxidation (i.e., oxidative cross-linking).

In accordance with various embodiments described herein, the drugrelease coatings of the present invention are formed of a fattyacid-derived biomaterial, which can be derived from saturated andunsaturated fatty acid compounds (e.g., free fatty acids, fatty acidester, monoglycerides, diglycerides, triglycerides, metal salts, etc.).Preferably, the source of fatty acids described in this invention issaturated and unsaturated fatty acids such as those readily available intriglyceride form in various oils (e.g., fish oils). One method of theformation of a fatty acid-derived biomaterial is accomplished throughautoxidation of the oil. As a liquid oil containing unsaturated fattyacid is heated, autoxidation occurs with the absorption of oxygen intothe oil to create hydroperoxides in an amount dependent upon the amountof unsaturated (C═C) sites in the oil. However, the (C═C) bonds are notconsumed in this initial reaction. Concurrent with the formation ofhydroperoxides is the isomerization of (C═C) double bonds from cis totrans in addition to double bond conjugation. Continued heating of theoil results in the solidifying of the coating through the formation ofcross-linking and by the further reaction of the hydroperoxides and thecleavage of C═C double bonds, which convert them into secondaryoxidation byproducts including aldehydes, ketones, alcohols, fattyacids, esters, lactones, ethers, and hydrocarbons which can eitherremain within the coating and/or are volatilized during the process.

The type and amount of cross-links formed during oil oxidation can betailored depending on the conditions selected (e.g., coating thickness,temperature, metal composition, etc.). For instance, heating of the oilallows for cross-linking between the fish oil unsaturated chains using acombination of peroxide (C—O—O—C), ether (C—O—C), and hydrocarbon (C—C)bridges (see, e.g., F. D. Gunstone, “Fatty Acid and Lipid Chemistry.”1999.). However, heating at lower temperatures (i.e., below 150° C.)results in the formation of predominantly peroxide cross-links whereheating at higher temperatures (i.e., above 150° C.) results in thethermal degradation of peroxides and C═C and ether cross-links dominate(F. D. Gunstone, 1999). Schematic illustrations of various cross-linkingmechanisms and schemes are shown in FIGS. 1-2.

In addition to thermal curing processes, oxidation of oils can also beinduced by light (e.g., photo-oxygenation). Photo-oxygenation is limitedto C═C carbon atoms and results in a conversion from cis to trans C═Cisomers during curing (as occurs with heat initiated curing). However,photo-oxygenation using UV is a relatively quicker reaction thanautoxidation from heat curing, in the realm of about 1000-1500 timesfaster. The quicker reaction especially holds true for methyleneinterrupted polyunsaturated fatty acids, such as EPA and DHA, which arefound in the fish oil based embodiments of the present invention.

An important aspect of UV curing when compared to heat curing is thatalthough the byproducts obtained by both curing methods are similar,they are not necessarily identical in amount or chemical structure. Onereason for this is due to the ability of photo-oxygenation to createhydroperoxides at more possible C═C sites.

Photo-oxygenation, such as that which results from UV curing, due to itsenhanced ability to create inner hydroperoxides, also results in theability to form relatively greater amounts of cyclic byproducts, whichalso relates to peroxide cross-linking between fish oil hydrocarbonchains. For example, photo-oxygenation of linolenate results in 6different types of hydroperoxides to be formed, whereas autoxidationresults in only 4. The greater amount of hydroperoxides created usingphoto-oxygenation results in a similar, but slightly different,structure and amount of secondary byproducts to be formed relative toautoxidation from heat curing. Specifically, these byproducts arealdehydes, ketones, alcohols, fatty acids, esters, lactones, ethers, andhydrocarbons.

Depending on the oil curing conditions and the fatty acid composition ofthe starting oil, a fatty acid-derived biomaterial can be produced bycuring the oil so as to oxidize the double bonds of the unsaturatedfatty acid chains while predominantly preserving triglyceride esterfunctional groups. The oxidation of the unsaturated fatty acid chainsresults in the formation of hydroperoxides, which, with continuedcuring, are converted into and aldehydes, ketones, alcohols, fattyacids, esters, lactones, ethers, and hydrocarbons. With continuedheating of the oxidized oil, the byproducts are volatilized, resultingin an increase in the coating viscosity in addition to the formation ofester cross-links. The formation of ester and lactone cross-links canoccur via different types of mechanisms (i.e., esterification,alcoholysis, acidolysis, interesterification as described in F. D.Gunstone, 1999, Chapter 8, incorporated herein by reference) between thehydroxyl and carboxyl functional components in the coating formed fromthe oxidation process (i.e., glyceride and fatty acid). Thecross-linking reaction can form different types of ester linkages suchas ester, anhydride, aliphatic peroxide, and lactones. FIGS. 3-4summarize the mechanism for the formation of the oil derived biomaterialand reaction chemistry, respectively. FIG. 5 provides a schematic ofdifferent methods to form esters from oils reaction schemes forillustrative purposes, but is not meant to be limiting in its scope tothe invention.

Fatty acid-derived biomaterial coatings and stand-alone films of thepresent invention are formed from an oil component. The term “oilcomponent” is also referred to herein as the “oil acid-containingstarting material” or “fatty acid-containing starting material.” The“fatty acid-containing starting material” may be natural or derived fromsynthetic sources. Preferably, the “oil containing starting material”comprises unsaturated fatty acids. The oil component can be either anoil, or an oil composition. The oil component can be a naturallyoccurring oil, such as fish oil, flax seed oil, grape seed oil, palmoil, a synthetic oil, or other oils having desired characteristics. Theoil can also be a synthetic oil. One embodiment of the present inventionmakes use of a fish oil in part because of the high content of omega-3fatty acids, which can provide healing support for damaged tissue, asdiscussed herein. The fish oil can also serve as an anti-adhesion agent.In addition, the fish oil maintains anti-inflammatory ornon-inflammatory properties as well. The present invention is notlimited to formation of the fatty acid-derived biomaterial with fish oilas the oil. However, the following description makes reference to theuse of fish oil as one example embodiment. Other naturally occurringoils or synthetic oils can be utilized in accordance with the presentinvention as described herein.

Coating Hydrolysis and Bioabsorption Chemistry of Fatty Acid-DerivedBiomaterials

Biodegradable and bioabsorbable implantable materials with ester,lactone, and anhydride functional groups are typically broken down byeither chemical and/or enzymatic hydrolysis mechanisms (K. Park et al.,“Biodegradable Hydrogels for Drug Delivery.” 1993; J. M. Andersen,“Perspectives on the In-Vivo Responses of Biodegradable Polymers.” inBiomedical Applications of Synthetic Biodegradable Polymers, edited byJeffrey O. Hollinger. 1995, pgs 223-233). Chemical hydrolysis of a fattyacid-derived biomaterial occurs when the functional group present in thematerial is cleaved by water. An example of chemical hydrolysis of atriglyceride under basic conditions is presented in FIG. 6. Enzymatichydrolysis is the cleavage of functional groups in a fatty acid-derivedbiomaterial caused by the reaction with a specific enzyme (i.e.,triglycerides are broken down by lipases (enzymes) that result in freefatty acids that can than be transported across cell membranes). Thelength of time a biodegradable and/or biodegradable fatty acid-derivedbiomaterial takes to be hydrolyzed is dependent on several factors suchas the cross-linking density of the material, the thickness, thehydration ability of the coating, the crystallinity of the fattyacid-derived biomaterial, and the ability for the hydrolysis products tobe metabolized by the body (K. Park et al., 1993 and J. M. Andersen,1995).

It should be noted that a bio-absorbable substance is different from abiodegradable substance. Biodegradable is generally defined as capableof being decomposed by biological agents, or capable of being brokendown by microorganisms or biological processes. Biodegradable substancescan cause inflammatory response due to either the parent substance orthose formed during hydrolysis, and they may or may not be absorbed bytissues. Some biodegradable substances are limited to bulk erosionmechanism for hydrolysis. For example, a commonly used biodegradablepolymer, PLGA (poly(lactic-co-glycolic acid)) undergoes chemicalhydrolysis in-vivo to form two alpha-hydroxy acids, specificallyglycolic and lactic acids. Although glycolic and lactic acids arebyproducts of various metabolic pathways in the body, it has beenpreviously demonstrated in previous medical implant and local drugdelivery applications that a local concentration of these productsresults in an acidic environment to be produced, which can lead toinflammation and damage to local tissue (S. Dumitriu, “PolymericBiomaterials.” 2002). Clinically, this can lead to impaired clinicaloutcomes such as restenosis (D. E. Drachman and D. I. Simon. CurrentAtherosclerosis Reports. 2005, Vol 7, pgs 44-49; S. E. Goldblum et al.Infection and Immunity. 1989, Vol. 57, No. 4, pgs 1218-1226) andimpaired healing in a coronary stent application which can lead tolate-stent thrombosis or adhesion formation in an abdominal herniarepair (Y. C. Cheong et al. Human Reproduction Update. 2001; Vol. 7, No.6: pgs 556-566). Thus, an ideal fatty acid-derived biomaterial shouldnot only demonstrate excellent biocompatibility upon implantation, butshould also maintain that biocompatibility during the life of itsimplantation with its hydrolysis byproducts being absorbable by localtissue.

The bio-absorbable nature of the fatty acid-derived biomaterials used asa stand-alone film, a coating for a medical device, or in drug deliveryapplications results in the biomaterial being absorbed over time by thecells of the body tissue. In various embodiments, there aresubstantially no substances in the coating, or in vivo conversionby-products of the coating, which induce an inflammatory response, e.g.,the coating converts in vivo into non-inflammatory components. Forexample, in various embodiments, the coatings of the present inventionupon absorption and hydrolysis do not produce lactic acid and glycolicacid break-down products in measurable amounts. The chemistry of thefatty acid-derived biomaterial described in this invention consists ofpredominantly fatty acid and glyceride components, which can either behydrolyzed in-vivo by chemical and/or enzymatic means, and which resultsin the release of fatty acid and glyceride components that can betransported across cell membranes. Subsequently, the fatty acid andglyceride components eluted from the fatty acid-derived biomaterial aredirectly metabolized by cells (i.e., they are bio-absorbable). Thebio-absorbable nature of the coating and stand-alone film of the presentinvention results in the coating being absorbed over time, leaving onlyan underlying delivery or other medical device structure that isbiocompatible. There is substantially no foreign body inflammatoryresponse to the bio-absorbable coating or its hydrolysis hydrolysisproducts in the preferred embodiments of the present invention.

Fatty Acid-Derived Biomaterial Biocompatibility and In-Vivo Performance

The process of making the fatty acid-derived biomaterials (e.g., coatingor stand-alone film) as described in this invention led to someunexpected chemical processes and characteristics in view of traditionalscientific reports in the literature about the oxidation of oils (J.Dubois et al. JAOCS. 1996, Vol. 73, No. 6., pgs 787-794. H. Ohkawa etal., Analytical Biochemistry, 1979, Vol. 95, pgs 351-358.; H. H. Draper,2000, Vol. 29, No. 11, pgs 1071-1077). Oil oxidation has traditionallybeen of concern for oil curing procedures due to the formation ofreactive byproducts such as hydroperoxides and alpha-beta unsaturatedaldehydes that are not considered to be biocompatible (H. C. Yeo et al.Methods in Enzymology. 1999, Vol. 300, pgs 70-78.; S-S. Kim et al.Lipids. 1999, Vol. 34, No. 5, pgs 489-496.). However, the oxidation offatty acids from oils and fats are normal and important in the controlof biochemical processes in-vivo. For example, the regulation of certainbiochemical pathways, such as to promote or reduce inflammation, iscontrolled by different lipid oxidation products (V. N. Bochkov and N.Leitinger. J. Mol. Med. 2003; Vol. 81, pgs 613-626). Additionally,omega-3 fatty acids are known to be important for human health andspecifically EPA and DHA are known to have anti-inflammatory propertiesin-vivo. However, EPA and DHA are not anti-inflammatory themselves, butit is the oxidative byproducts they are biochemically converted intothat produce anti-inflammatory effects in-vivo (V. N. Bochkov and N.Leitinger, 2003; L. J. Roberts II et al. The Journal of BiologicalChemistry. 1998; Vol. 273, No. 22, pgs 13605-13612.). Thus, althoughthere are certain oil oxidation products that are not biocompatible,there are also several others that have positive biochemical propertiesin-vivo (V. N. Bochkov and N. Leitinger, 2003; F. M. Sacks and H.Campos. J Clin Endocrinol Metab. 2006; Vol. 91, No. 2, pgs 398-400; A.Mishra et al. Arterioscler Thromb Vasc Biol. 2004; pgs 1621-1627.).Thus, by selecting the appropriate process conditions, a cross-linkedhydrophobic fatty acid-derived biomaterial (from, e.g., fish oil) can becreated and controlled using oil oxidation chemistry with a finalchemical profile that will have a favorable biological performancein-vivo.

The process of making a fatty acid-derived hydrophobic non-polymericbiomaterial as described in this invention leads to a final chemicalprofile that is biocompatible, minimizes adhesion formation, acts as atissue separating barrier, and is non-inflammatory with respect to thematerial chemistry and the products produced upon hydrolysis andabsorption by the body in-vivo. The reason for these properties is dueto several unique characteristics of the fatty acid-derived biomaterials(e.g., coatings or stand-alone films) of the invention.

One important aspect of the invention is that no toxic, short-chainedcross-linking agents (such as glutaraldehyde) are used to form the fattyacid-derived biomaterials (e.g., coatings or stand-alone films) of theinvention. It has been previously demonstrated in the literature thatshort chain cross-linking agents can elute during hydrolysis ofbiodegradable polymers and cause local tissue inflammation. The processof creating fatty acid-derived biomaterials does not involve addingexternal cross-linking agents because the oil is solely cured into acoating using oil autoxidation or photo-oxidation chemistry. Theoxidation process results in the formation of carboxyl and hydroxylfunctional groups that allow for the fatty acid-derived biomaterial tobecome hydrated and become slippery, which allows for frictional injuryduring and after implantation to be significantly reduced and/oreliminated. The methods of making the fatty acid-derived biomaterialsdescribed herein allow the alkyl chains of the fatty acid, glyceride andother lipid byproducts present in the coating to be disordered, whichcreates a coating that is flexible and aids in handling of the materialwhile being implanted.

There are several individual chemical components of the coating that aidin its biocompatibility and its low to non-inflammatory responseobserved in-vivo. One critical aspect is that the process of creating afatty acid-derived biomaterial as described herein results in low tonon-detectable amounts of oxidized lipid byproducts of biocompatibilityconcern, such as aldehydes. These products are either almost completelyreacted or volatilized during the curing process as described in thisinvention. The process of creating a fatty acid-derived biomateriallargely preserves the esters of the native oil triglycerides and formsester and/or lactone cross-links, which are biocompatible (K. Park etal., 1993; J. M. Andersen, 1995).

In addition to general chemical properties of a fatty acid-derivedbiomaterial that assists in its biocompatibility, there are alsospecific chemical components that have positive biological properties.Another aspect is that the fatty acid chemistry produced upon creationof a fatty acid-derived biomaterial is similar to the fatty acidchemistry of tissue, as presented in FIG. 7. Thus, as fatty acids areeluting from the coating they are not viewed as being “foreign” by thebody and cause an inflammatory response. In fact, C14 (myristic) and C16(palmitic) fatty acids present in the coating have been shown in theliterature to reduce production of α-TNF, an inflammatory cytokine. Theexpression of α-TNF has been identified as one of the key cytokinesresponsible for “turning on” inflammation in the peritoneal after herniarepair, which can then lead to abnormal healing and adhesion formation(Y. C. Cheong et al., 2001). α-TNF is also an important cytokine invascular injury and inflammation (D. E. Drachman and D. T. Simon, 2005;S. E. Goldblum, 1989), such as vascular injury caused during a stentdeployment. In addition to the fatty acids just specified, there havealso been additional oxidized fatty acids identified that haveanti-inflammatory properties. Another component identified from thefatty acid-derived coatings as described in this invention isdelta-lactones (i.e., 6-membered ring cyclic esters). Delta-lactoneshave been identified as having anti-tumor properties (H. Tanaka et al.Life Sciences 2007; Vol. 80, pgs 1851-1855).

These components identified are not meant to be limiting in scope tothis invention as changes in starting oil composition and/or processconditions can invariably alter the fatty acid and/or oxidativebyproduct profiles and can be tailored as needed depending on theintended purpose and site of application of the fatty acid-derivedbiomaterial.

In summary, the biocompatibility and observed in in-vivo performance offatty acid-derived biomaterials described in this invention is due tothe elution of fatty acids during hydrolysis of the material duringimplantation and healing and is not only beneficial as to prevent aforeign body response in-vivo due to the similarity of the fatty acidcomposition of the material to native tissue (i.e., a biological“stealth” coating), but the specific fatty acids and/or other lipidoxidation components eluting from the coating aid in preventing foreignbody reactions and reducing or eliminating inflammation, which leads toimproved patient outcomes. Additionally, the fatty acid and glyceridecomponents eluted from the fatty acid-derived biomaterial are able to beabsorbed by local tissue and metabolized by cells, in, for example, theCitric Acid Cycle (M. J. Campell, “Biochemistry: Second Edition.” 1995,pgs 366-389). Hence, the fatty acid-derived biomaterial (e.g., coatingor stand-alone film) described in this invention is also bioabsorbable.

Accordingly, in one aspect, the invention provides a bio-absorbable,fatty acid-based coating for a medical device, comprising a cross-linkedfatty acid fatty acid-derived biomaterial and a therapeutic agent. Theinvention also provides a bio-absorbable, fatty acid-based stand-alonefilm, comprising a cross-linked fatty acid fatty acid-derivedbiomaterial and a therapeutic agent. The coating and stand-alone filmcan be prepared according to the methods discussed herein.

Methods of Treatment Using Fatty Acid-Derived Materials

Also provided herein is a fatty acid-based biomaterial suitable fortreating or preventing disorders related to vascular injury and/orvascular inflammation. The fatty acid-based biomaterial can also be usedto treat or prevent injury to tissue, e.g., soft tissue. The fattyacid-based biomaterial can be a coating for a medical device or astand-alone film. In another embodiment, the source of the fatty acidfor the biomaterial is an oil, such as fish oil.

In general, four types of soft tissue are present in humans: epithelialtissue, e.g., the skin and the lining of the vessels and many organs;connective tissue, e.g., tendons, ligaments, cartilage, fat, bloodvessels, and bone; muscle, e.g., skeletal (striated), cardiac, orsmooth; and nervous tissue, e.g., brain, spinal chord and nerves. Thefatty acid-based biomaterial of the invention (e.g., stand-alone film)can be used to treat injury to these soft tissue areas. Thus, in oneembodiment, the fatty acid-based biomaterial of the invention (e.g.,stand-alone film) can be used for promotion of proliferation of softtissue for wound healing. Furthermore, following acute trauma, softtissue can undergo changes and adaptations as a result of healing andthe rehabilitative process. Such changes include, by are not limited to,metaplasia, which is conversion of one kind of tissue into a form thatis not normal for that tissue; dysplasia, with is the abnormaldevelopment of tissue; hyperplasia, which is excessive proliferation ofnormal cells in the normal tissue arrangement; and atrophy, which is adecrease in the size of tissue due to cell death and resorption ordecreased cell proliferation. Accordingly, the fatty acid-basedbiomaterial of the invention (e.g., stand-alone film) can be used forthe diminishment or alleviation of at least one symptom associated withor caused by acute trauma in soft tissue.

In one embodiment, as described below, the fatty acid-based biomaterialcan be used, for example, to prevent tissue adhesion. The tissueadhesion can be a result of blunt dissection. Blunt dissection can begenerally described as dissection accomplished by separating tissuesalong natural cleavage lines without cutting. Blunt dissection isexecuted using a number of different blunt surgical tools, as isunderstood by those of ordinary skill in the art. Blunt dissection isoften performed in cardiovascular, colo-rectal, urology, gynecology,upper GI, and plastic surgery applications, among others.

After the blunt dissection separates the desired tissues into separateareas, there is often a need to maintain the separation of thosetissues. In fact, post surgical adhesions can occur following almost anytype of surgery, resulting in serious postoperative complications. Theformation of surgical adhesions is a complex inflammatory process inwhich tissues that normally remain separated in the body come intophysical contact with one another and attach to each other as a resultof surgical trauma.

It is believed that adhesions are formed when bleeding and leakage ofplasma proteins from damaged tissue deposit in the abdominal cavity andform what is called a fibrinous exudate. Fibrin, which restores injuredtissues, is sticky, so the fibrinous exudate may attach to adjacentanatomical structures in the abdomen. Post-traumatic or continuousinflammation exaggerates this process, as fibrin deposition is a uniformhost response to local inflammation. This attachment seems to bereversible during the first few days after injury because the fibrinousexudates go through enzymatic degradation caused by the release offibrinolytic factors, most notably tissue-type plasminogen activator(t-PA). There is constant play between t-PA and plasminogen-activatorinhibitors. Surgical trauma usually decreases t-PA activity andincreases plasminogen-activator inhibitors. When this happens, thefibrin in the fibrinous exudate is replaced by collagen. Blood vesselsbegin to form, which leads to the development of an adhesion. Once thishas occurred, the adhesion is believed to be irreversible. Therefore,the balance between fibrin deposition and degradation during the firstfew days post-trauma is critical to the development of adhesions(Holmdahl L. Lancet 1999; 353: 1456-57). If normal fibrinolytic activitycan be maintained or quickly restored, fibrous deposits are lysed andpermanent adhesions can be avoided. Adhesions can appear as thin sheetsof tissue or as thick fibrous bands.

Often, the inflammatory response is also triggered by a foreignsubstance in vivo, such as an implanted medical device. The body seesthis implant as a foreign substance, and the inflammatory response is acellular reaction to wall off the foreign material. This inflammationcan lead to adhesion formation to the implanted device; therefore amaterial that causes little to no inflammatory response is desired.

Thus, the fatty acid-based biomaterial (e.g., stand-alone film) of thepresent invention may be used as a barrier to keep tissues separated toavoid the formation of adhesions, e.g., surgical adhesions. Applicationexamples for adhesion prevention include abdominal surgeries, spinalrepair, orthopedic surgeries, tendon and ligament repairs, gynecologicaland pelvic surgeries, and nerve repair applications. The fattyacid-based biomaterial (e.g., stand-alone film) may be applied over thetrauma site or wrapped around the tissue or organ to limit adhesionformation. The addition of therapeutic agents to the fatty acid-basedbiomaterial used in these adhesion prevention applications can beutilized for additional beneficial effects, such as pain relief orinfection minimization. Other surgical applications of the fattyacid-based biomaterial may include using a stand-alone film as a durapatch, buttressing material, internal wound care (such as a graftanastomotic site), and internal drug delivery system. The fattyacid-based biomaterial may also be used in applications in transdermal,wound healing, and non-surgical fields. The fatty acid-based biomaterialmay be used in external wound care, such as a treatment for burns orskin ulcers. The fatty acid-based biomaterial may be used without anytherapeutic agent as a clean, non-permeable, non-adhesive,non-inflammatory, anti-inflammatory dressing, or the fatty acid-basedbiomaterial may be used with one or more therapeutic agents foradditional beneficial effects. The fatty acid-based biomaterial may alsobe used as a transdermal drug delivery patch when the fatty acid-basedbiomaterial is loaded or coated with one or more therapeutic agents.

The process of wound healing involves tissue repair in response toinjury and it encompasses many different biologic processes, includingepithelial growth and differentiation, fibrous tissue production andfunction, angiogenesis, and inflammation. Accordingly, the fattyacid-based biomaterial (e.g., stand-alone film) provides an excellentmaterial suitable for wound healing applications.

Modulated Healing

Also provided herein is a fatty acid-based biomaterial suitable forachieving modulated healing in a tissue region in need thereof, whereinthe composition is administered in an amount sufficient to achieve saidmodulated healing. In one embodiment, the fatty acid-based biomaterialis a coating for a medical device or a stand-alone film. In anotherembodiment, the source of the fatty acid for the biomaterial is an oil,such as fish oil.

Modulated healing can be described as the in-vivo effect observedpost-implant in which the biological response is altered resulting in asignificant reduction in foreign body response. As utilized herein, thephrase “modulated healing” and variants of this language generallyrefers to the modulation (e.g., alteration, delay, retardation,reduction, detaining) of a process involving different cascades orsequences of naturally occurring tissue repair in response to localizedtissue injury, substantially reducing their inflammatory effect.Modulated healing encompasses many different biologic processes,including epithelial growth, fibrin deposition, platelet activation andattachment, inhibition, proliferation and/or differentiation, connectivefibrous tissue production and function, angiogenesis, and several stagesof acute and/or chronic inflammation, and their interplay with eachother. For example, the fatty acids described herein can alter, delay,retard, reduce, and/or detain one or more of the phases associated withhealing of vascular injury caused by medical procedures, including, butnot limited to, the inflammatory phase (e.g., platelet or fibrindeposition), and the proliferative phase. In one embodiment, “modulatedhealing” refers to the ability of a fatty acid derived biomaterial toalter a substantial inflammatory phase (e.g., platelet or fibrindeposition) at the beginning of the tissue healing process. As usedherein, the phrase “alter a substantial inflammatory phase” refers tothe ability of the fatty acid derived biomaterial to substantiallyreduce the inflammatory response at an injury site. In such an instance,a minor amount of inflammation may ensue in response to tissue injury,but this level of inflammation response, e.g., platelet and/or fibrindeposition, is substantially reduced when compared to inflammation thattakes place in the absence of the fatty acid derived biomaterial.

For example, the fatty acid derived biomaterial (e.g., coating orstand-alone film) of the present invention has been shown experimentallyin animal models to delay or alter the inflammatory response associatedwith vascular injury, as well as excessive formation of connectivefibrous tissue following tissue injury. The fatty acid derivedbiomaterial (e.g., coating or stand-alone film) of the present inventioncan delay or reduce fibrin deposition and platelet attachment to a bloodcontact surface following vascular injury.

Accordingly, the fatty acid derived biomaterial (e.g., coating orstand-alone film) of the present invention provides an excellentabsorbable cellular interface suitable for use with a surgicalinstrument or medical device that results in a modulated healing effect,avoiding the generation of scar tissue and promoting the formation ofhealthy tissue at a modulated or delayed period in time following theinjury. Without being bound by theory, this modulated healing effect canbe attributed to the modulation (e.g., alteration, delay, retardation,reduction, detaining) of any of the molecular processes associated withthe healing processes of vascular injury. For example, the fatty acidderived biomaterial (e.g., coating or stand-alone film) of the presentinvention can act as a barrier or blocking layer between a medicaldevice implant (e.g., a surgical mesh, graft, or stent), or surgicalinstrument, and the cells and proteins that compose the vessel wall,such as the endothelial cells and smooth muscle cells that line thevessel's interior surface. The barrier layer prevents the interactionbetween the surgical implant and the vessel surface, thereby preventingthe initiation of the healing process by the cells and proteins of thevessel wall. In this respect, the barrier layer acts as a patch thatbinds to the vessel wall and blocks cells and proteins of the vesselwall from recognizing the surgical implant (i.e., the barrier layerblocks cell-device and/or protein-device interactions), thereby blockingthe initiation of the vascular healing process, and avoiding the fibrinactivation and deposition and platelet activation and deposition.

In another non-binding example, the modulated healing effect can beattributed to the modulation (e.g., alteration, delay, retardation,reduction, detaining) of signaling between the cells and proteins thatcompose the vessel wall and various components of the bloodstream thatwould otherwise initiate the vascular healing process. Stateddifferently, at the site of vascular injury, the fatty acid derivedbiomaterial (e.g., coating or stand-alone film) of the present inventioncan modulate the interaction of cells of the vessel wall, such asendothelial cells and/or smooth muscle cells, with other cells and/orproteins of the blood that would otherwise interact with the damagedcells to initiate the healing process. Additionally, at the site ofvascular injury, the fatty acid derived biomaterial (e.g., coating orstand-alone film) of the present invention can modulate the interactionof proteins of the vessel wall with other cells and/or proteins of theblood, thereby modulating the healing process.

The fatty acid derived biomaterial (e.g., coating or stand-alone film)of the present invention can be designed to maintain its integrity for adesired period of time, and then begin to hydrolyze and be absorbed intothe tissue that it is surrounded by. Alternatively, the fatty acidderived biomaterial can be designed such that, to some degree, it isabsorbed into surrounding tissue immediately after the fatty acidderived biomaterial is inserted in the subject. Depending on theformulation of the fatty acid derived biomaterial, it can be completelyabsorbed into surrounding tissue within a time period of 1 day to 24months, e.g., 1 week to 12 months, e.g., 1 month to 10 months, e.g., 3months to 6 months. Animal studies have shown resorption of the fattyacid derived biomaterial occurring upon implantation and continuing overa 3 to 6 month period, and beyond.

Tailoring of Drug Release Profiles

In various aspects, the present invention provides methods of curing afatty acid-derived coating, preferably fish oil, to provide a fattyacid-derived biomaterial coating or stand-alone film containing one ormore therapeutic agents that can tailor the release profile of atherapeutic agent from the coating or film. The release profile can betailored, e.g., through changes in fatty acid (e.g., oil, e.g., fishoil) chemistry by varying coating composition, temperature, and curetimes. The position of the drug-containing layer on the coated deviceprovides an additional mechanism to alter the release profile of thenon-polymeric cross-linked fatty acid-derived biomaterial coating. Thiscan be achieved, e.g., by loading a drug into a cured base coating layerand coating a topcoat overlayer cured coating onto the previously curedencapsulating base layer.

An advantage of the cured fish oil coating and stand-alone film invarious embodiments of the present invention is that the curingconditions utilized (i.e., cure time and temperature) can directlyinfluence the amount of coating cross-linking density and byproductformation, which in turn effects the coating degradation. Thus, byaltering the curing conditions employed, the dissolution rate of atherapeutic compound of interest contained in the coating can also bealtered.

In various embodiments, an agent, such as, e.g., a free radicalscavenger, can be added to the starting material to tailor the drugrelease profile of the fatty acid-derived biomaterial that is formed. Invarious embodiments, vitamin E is added to the starting material to, forexample, slow down autoxidation in fish oil by reducing hydroperoxideformation, which can result in a decrease in the amount of cross-linkingobserved in a cured fish oil coating. In addition, other agents can beused to increase the solubility of a therapeutic agent in the oilcomponent of the starting material, protect the drug from degradationduring the curing process, or both. For example, vitamin E can also beused to increase the solubility of certain drugs in a fish oil startingmaterial, and thereby facilitate tailoring the drug load of the eventualcured coating. Thus, varying the amount of vitamin E present in thecoating provides an additional mechanism to alter the cross-linking andchemical composition of the fatty acid-derived biomaterials (e.g.,coatings and stand-alone films) of the present invention.

In various embodiments, the present invention provides fattyacid-derived biomaterials (e.g., coatings and stand-alone films) wherethe drug release profile of the fatty acid-derived biomaterial istailored through the provision of two or more coatings and selection ofthe location of the therapeutic agent. The drug location can be altered,e.g., by coating a bare portion of a medical device with a firststarting material and creating a first cured coating, then coating atleast a portion of the first cured-coating with the drug-oil formulationto create a second overlayer coating. The first starting material cancontain one or more therapeutic agents. In various embodiments, thesecond overlayer coating is also cured. The drug load, drug releaseprofiles, or both, of the first coating, the overlay coating, or both,can be tailored through the use of different curing conditions and/oraddition of free radical scavengers (e.g., vitamin E), as describedherein. The process of providing two layers can be extended to providethree or more layers, wherein at least one of the layers comprises ahydrophobic, cross-linked fatty acid-derived biomaterial prepared from afatty-acid containing oil, such as fish oil. In addition, one or more ofthe layers can be drug eluting, and the drug release profile of suchlayers can be tailored using the methods described herein.

In various embodiments, the present invention provides coatings wherethe drug release profile of the overall coating is tailored through theprovision of two or more coating regions with different drug releaseprofiles and selection of the location of the therapeutic agent. Invarious embodiments, the formation of different coating regions withdifferent drug release properties is obtained by location specificcuring conditions, e.g., location specific UV irradiation, and/orlocation specific deposition of a starting material on the coateddevice, e.g., by ink jet printing methods.

Coating Approaches

FIG. 8 illustrates one method of making a medical device, such as, e.g.,a drug eluting coated stent, in accordance with one embodiment of thepresent invention. The process involves providing a medical device, suchas the stent (step 100). A non-polymeric cross-linked fatty acid-derivedbiomaterial coating is then applied to the medical device (step 102).One of ordinary skill in the art will appreciate that this basic methodof application of a coating to a medical device, such as a stent, canhave a number of different variations falling within the processdescribed. The step of applying a coating substance to form a coating onthe medical device can include a number of different applicationmethods. For example, the medical device can be dipped into a liquidsolution of the coating substance. The coating substance can be sprayedonto the device. Another application method is painting the coatingsubstance on to the medical device. One of ordinary skill in the artwill appreciate that other methods, such as electrostatic adhesion, canbe utilized to apply the coating substance to the medical device. Someapplication methods may be particular to the coating substance and/or tothe structure of the medical device receiving the coating. Accordingly,the present invention is not limited to the specific embodiments ofstarting material application described herein, but is intended to applygenerally to the application of the starting material which is to becomea fatty acid-derived biomaterial coating of a medical device, takingwhatever precautions are necessary to make the resulting coatingmaintain desired characteristics.

FIG. 9 is a flowchart illustrating one example implementation of themethod of FIG. 8. In accordance with the steps illustrated in FIG. 9, abio-absorbable carrier component formed from or of the non-polymericfatty acid-derived biomaterial of the present invention is providedalong with a therapeutic agent component (step 110). The provision ofthe bio-absorbable carrier component and the provision of thetherapeutic agent component can occur individually, or in combination,and can occur in any order or simultaneously. The bio-absorbable carriercomponent is mixed with the therapeutic agent component (or vice versa)to form a starting material which is to become a hydrophobic, fattyacid-derived biomaterial coating (step 112). The starting material isapplied to the medical device, such as the stent 10, to form the coating(step 114). The coating is then cured (step 116) by any of the curingmethods described herein to form a fatty acid-derived biomaterialcoating.

The coated medical device is then sterilized using any number ofdifferent sterilization processes (step 118). For example, sterilizationcan be implemented utilizing ethylene oxide, gamma radiation, E beam,steam, gas plasma, or vaporized hydrogen peroxide. One of ordinary skillin the art will appreciate that other sterilization processes can alsobe applied, and that those listed herein are merely examples ofsterilization processes that result in a sterilization of the coatedstent, preferably without having a detrimental effect on the coating.

It should be noted that the oil component or oil composition can beadded multiple times to create multiple tiers in forming the coating.For example, if a thicker coating is desired, additional tiers of theoil component or oil composition can be added. Different variationsrelating to when the oil is cured and when other substances are added tothe oil are possible in a number of different process configurations.Accordingly, the present invention is not limited to the specificsequence illustrated. Rather, different combinations of the basic stepsillustrated are anticipated by the present invention.

FIGS. 10A-10E illustrate some of the other forms of medical devicesmentioned above in combination with the coating 10 of the presentinvention. FIG. 10A shows a graft 50 with the coating 10 coupled oradhered thereto. FIG. 10B shows a catheter balloon 52 with the coating10 coupled or adhered thereto. FIG. 10C shows a stent 54 with thecoating 10 coupled or adhered thereto. FIG. 10D illustrates a stent 10in accordance with one embodiment of the present invention. The stent 10is representative of a medical device that is suitable for having acoating applied thereon to effect a therapeutic result. The stent 10 isformed of a series of interconnected struts 12 having gaps 14 formedtherebetween. The stent 10 is generally cylindrically shaped.Accordingly, the stent 10 maintains an interior surface 16 and anexterior surface 18. FIG. 10E illustrates a coated surgical mesh,represented as a biocompatible mesh structure 10, in accordance with oneembodiment of the present invention. The biocompatible mesh structure 10is flexible, to the extent that it can be placed in a flat, curved, orrolled configuration within a patient. The biocompatible mesh structure10 is implantable, for both short term and long term applications.Depending on the particular formulation of the biocompatible meshstructure 10, the biocompatible mesh structure 10 will be present afterimplantation for a period of hours to days, or possibly months, orpermanently.

Each of the medical devices illustrated, in addition to others notspecifically illustrated or discussed, can be combined with the coating10 using the methods described herein, or variations thereof.Accordingly, the present invention is not limited to the exampleembodiments illustrated. Rather the embodiments illustrated are merelyexample implementations of the present invention.

Various aspects and embodiments are further described by way of thefollowing Examples. The Examples are offered by way of illustration andnot by way of limitation.

EXAMPLES

The following examples characterize the hydrophobic cross-linked fattyacid-derived biomaterial chemistry described in this invention andillustrate some of the boundaries associated with the chemicalmechanisms of formation and how alteration of those mechanismsinfluences the properties (e.g., therapeutic benefits and/or drugrelease profile) of the final product. The identity of some of thehydrolysis products are identified through in-vitro experiments andcorrelated with in-vivo experiments to demonstrate the ability for thecoating or stand-alone film to be bioabsorbed. Finally, examples showingthe utility of the fatty acid-derived biomaterials described in thisinvention in drug delivery applications on coronary stents and herniamesh devices are presented.

The following examples are for demonstration purposes and are not meantto be limiting.

Example 1: Characterization of a Novel Biomaterial Derived from Fish Oil

In this example, coated medical devices (e.g., a polypropylene mesh)were cured in a high airflow oven at 200° F. for 24 hours, after whichthe fish oil was converted into a cross-linked biomaterial coatingencapsulating the polypropylene mesh by oxidation of the C═C bondspresent in the fish oil resulting in the formation of oxidativebyproducts (i.e., hydrocarbons, aldehydes, ketones, glycerides, fattyacids) while largely preserving the esters derived from the original oiltriglycerides. Volatilization of the byproducts followed by theformation of ester and lactone cross-links result in the solidificationof oil into a bioabsorbable hydrophobic cross-linked fatty acid-derivedbiomaterial. FTIR, X-ray diffraction, and GC-FID fatty acidcompositional analysis and GC-MS were performed on the fish oil derivedcoatings to characterize its chemistry.

FTIR Analysis:

FIG. 11 is an FTIR analysis, which illustrates a comparison of theuncured fish oil (801) with the final cured fatty acid-derivedbiomaterial. The FTIR shows that the coating contained hydroxyl (800),methylene (805), trans C═C (810), and lactone/ester bonds (815 and 830).A complex carbonyl band shape was obtained and determined to containester (820), ketone (825), aldehyde (825), and fatty acid (825)absorptions in addition to detecting the presence of cross-linking(830). Although several different types of ester cross-linking arepossible (e.g, anhydride, lactone, aliphatic peroxide, etc.) thebroadness of the lactone/band suggests a combination of lactone (cyclicester) and ester (R—C═C—O—CO-Alkyl) functional groups predominate sincethere is a single cross-linking peak absorption from 1740-1840 cm⁻¹. Incontrast, anhydride (CO—O—CO) and aliphatic peroxides (CO—O—O—CO) bothhave two carbonyls and would be expected to have two peaks withabsorptions around approximately 1850-1800 and 1790-1740 cm⁻¹.Additionally, evaluation of the fish oil and fatty acid-derivedbiomaterial ester (820) absorption bands show that there is not asignificant reduction in ester band height after curing, indicating thatthe original triglyceride ester groups are largely preserved through thecuring process. The position of the methylene bands showed that thehydrocarbon chains present in the coating were in a disordered state(position above about 2918 cm⁻¹), which is consistent with anon-crystalline structure. This result was also confirmed by X-raydiffraction results which showed that the fatty acid-derived biomaterialcoating is amorphorous (i.e., disordered). Further, the cis C═C bonds inthe fish oil starting material (835) were observed to be almost entirelyconsumed during the curing process. There was an increase in the transC═C bonds (810) during the curing process, but is reduced in peak areain comparison to the original cis C═C band, which is consistent with theoxidation of the C═C bonds in the oil during the curing process.

FTIR spectra were also acquired kinetically during the curing processusing a procedure described in the literature (see, e.g., Van de Voortet al. (1994) JAOCS, vol 70, no. 3, pgs 243-253, the entire contents ofwhich is hereby incorporated by reference) to monitor changes in thechemistry of the coating during the curing of the fatty acid-derivedbiomaterial using normalized peak height ratios. FIG. 12A compares thechange in the normalized peak height of the OH, glyceride ester, andlactone/ester as a function of temperature. The data in FIG. 12A shows asharp increase in the OH band up to hour 11, after which the OH banddramatically decreases through the rest of the curing process. Thiscorrelates with the increase in the lactone/ester cross-linking bandwhich also dramatically increases around hours 10-11, at which point thecoating is observed to physically convert into a gel. Additionally atthis same time interval, the C═C bonds have isomerized from a cis totrans configuration, which would assist in facilitating the formation ofester and lactone linkages (i.e., esterification between hydroxyl andcarboxyl functional groups in oxidized fatty acids and glyceridespresent in the oil (FIG. 12B)). Also, after hour 11 the trans C═C bonddecreases as the curing process continues, which indicates that the C═Cbonds are being oxidized. By the end of the curing process the trans C═Cband is approximately half of the peak area of original cis C═C bonds.Finally, using the subtraction technique mentioned by Van de Voort etal. it is possible to resolve a small amount of thermal hydrolysis inthe native glyceride band, followed by esterification during the curingreaction using normalized peak height measurements (FIG. 12A). However,as mentioned previously, the overall peak height in the glyceride peakheight before and after curing without subtraction and normalizationremains largely unchanged (FIG. 11).

GC-FID Fatty Acid Compositional Analysis:

GC fatty acid profile analysis was conducted on the fish oil and a fishfatty acid-derived biomaterial using the official AOCS method Ce 1b-89,as presented in FIG. 13. It is important to note that the fattyacid-derived biomaterial coating completely saponified using theconditions outlined in the AOCS procedure. The GC fatty acid profiledata proves that the C═C bonds of the fatty acids present in thebiomaterial are oxidized and cleaved during the curing process as thepolyunsaturated fatty acids are significantly reduced and onlymonounsaturated and saturated fatty acids are detected. The longerpolyunsatured fatty acids (above C20-1 (i.e., twenty carbons, one doublebond)) are significantly reduced to non-detected after the curingprocess. This contrasts a hydrogenation process where C═C bonds areconverted into CH₂—CH₂ functional groups without any reduction in thechain length of the fatty acids present (i.e., C20-5 would become C20-0with a similar peak area %).

GC-MS Compositional Analysis:

GC-MS compositional analysis was conducted on the fatty acid derived(from fish oil) biomaterial. The biomaterial was dissolved in THF at 65°C. and the soluble component was filtered away from the insolublecomponent. Using this process it was determined that 68% of the coatingwas insoluble in THF and composed of cross-linked fatty acid andglycerides. The other 32% (soluble portion) of the coating was assayedusing GC-MS and the identity and amount of different byproducts weredetermined, as presented in FIG. 14. The GC-MS showed that over 90% ofthe THF soluble components detected and identified were fatty acids andglycerides where only ˜5% of the byproducts were identified asindividually being either aldehydes or ketones. Finally, in a separateexperiment, GC-MS analysis was conducted using hexane extraction for 24hours at 37° C. In addition to the products already identified in FIG.14, approximately 150-300 ppm of 3 different delta-lactones were alsodetected.

Example 2: Characterization of Novel Biomaterials Derived from Other OilStarting Materials

In Example 2, separate coated medical devices were cured in a highairflow oven at 200° F. for 24 hours, using flax seed, fish, grape seed,or olive oils as the starting material in order to determine the effectsof initial fatty acid starting chemistry on the ability to form anon-polymeric, fatty acid-derived hydrophobic biomaterial coating by theoxidative cross-linking mechanisms described in Example 1. After thecuring process, the physical properties of each fatty acid-derivedcoating were noted in addition to being analyzed using FTIR, GC-FIDfatty acid profile, and GC-FID aldehyde assay testing.

Physical Properties:

Table 2 presents a summary of the physical properties observed in eachoil coating after curing at 200° F. for 24 hours.

TABLE 2 Oil Coating Physical Properties Olive Oil Liquid Grape seed OilSlightly sticky Flax seed Oil Dry coating Fish Oil Dry coating

FTIR Analysis:

FIG. 15 shows the FTIR spectra of the carbonyl absorption region afterthe 200° F. curing process for the olive, flax seed, grape seed and fishfatty acid-derived biomaterials. The FTIR spectra of the carbonyl bandregion correlate with the physical properties observed in Table 2. Theolive oil, which is liquid, does not show any detectable amount oflactone/ester cross-linking from 1755-1840 cm⁻¹. This contrasts theother oils which show varying amounts of cross-linking, with fish oilhaving the most cross-linking under the conditions employed. FIG. 16shows a plot of normalized peak ratios for cis and trans C═C,lactone/ester cross-linking, and fatty acid byproducts from the FTIRspectra presented in FIG. 15. The data in FIG. 16 shows that usingdifferent starting oils with the same curing process, the finalchemistry of the products can be altered, however, for olive oil, whichdoes not make a cured fatty acid-derived biomaterial coating under theseprocess conditions, the peak ratios are significantly different incomparison to the fish, flaxseed, and grape seed oil biomaterialcoatings.

GC-FID Fatty Acid Compositional Analysis:

GC fatty acid profile analysis was conducted on the fish oil and fishfatty acid-derived hydrophobic cross-linked gel using the official AOCSmethod Ce 1-89b, as presented in FIGS. 17-18. For the grape seed, fish,and flax seed oils a significant difference in fatty acid compositionbefore and after curing is observed. Specifically, the long chainpolyunsaturated fatty acids are oxidized during the curing process whereonly predominantly saturated and unsaturated fatty acids are detected(FIGS. 17 and 18A). In contrast, for the olive oil (FIG. 18B) there isvery little relative change in the initial and final fatty acidcompositional analysis. The difference in the starting fatty acidcomposition between the olive oil and the rest of the oils is thestarting polyunsaturated fatty acid composition. Olive oil only has only9% polyunsaturated fatty acids where all the rest of the oils have atleast 40% or greater.

GC-FID Aldehyde Assay Analysis:

GC aldehyde assay was performed on each biomaterial coating byextracting the sample in hexane for either 1 hr or 24 hrs at 37° C. andinjecting the liquid solution neat into the GC. The aldehydes werequantified using an external standard curve. Previous GC-MS experimentsallowed for the aldehyde identities to be determined in order to selectthe appropriate external standards to be used for quantification.Initial testing involved extracting the fish oil derived biomaterial inhexane for 1 hr and dilution of olive oil in hexane since it remainedliquid after cure. The results of this extraction experiment showed thataldehydes could easily be quantified from the olive oil sample, butcould not be detected from the fish oil coating after only 1 hr ofextraction in hexane. Exhaustive extraction in hexane of the fish oil,grape seed, and flax seed oils was performed for 24 hours at 37° C. Thetotal amount of aldehydes for the fish, grape seed, and flax seed oilswere over an order of magnitude less than was detected in the olive oil.

TABLE 3 Aldehyde Assay Results from Different Oil Derived Biomaterialsafter Extraction in Hexane for 1 hr. Oil Coating Total Aldehyde AmountsOlive Oil 3481 ppm Fish Oil Non-detectable (i.e. <1 ppm)

TABLE 4 Aldehyde Assay Results from Different Oil Derived Biomaterialsafter Exhaustive Extraction on Hexane for 24 hrs. Oil Coating TotalAldehyde Amounts Grape Seed Oil 151 ppm Flax Seed Oil 228 ppm Fish Oil254 ppm

Fatty Acid Ranges for Various Oils:

Flax seed, grape seed, and fish fatty acid-derived biomaterials wereprepared in accordance with the procedures of this example. GC fattyacid profile analysis showed the following fatty acid ranges:

Flax seed fatty acid-derived biomaterial C16:0  5-30% C18:0  0-15% C18:115-40% C18:2  0-20% C18:3  0-60% Grape seed fatty acid-derivedbiomaterial C16:0  5-30% C18:0  0-20% C18:1 15-30% C18:2  0-75% Fishfatty acid-derived biomaterial C14:0  5-25% C16:0  5-50% C16:1  5-15%C18:0  0-10% C18:1  5-20% C18:2  0-5% C18:3  0-5% C20:1  0-5% C20:4 0-5% C20:5  0-40% C22:6  0-30% C24:1  0-2%

Conclusions:

This set of experiments showed that, in order to create a fatty acidderived biomaterial (e.g., coating or stand-alone film), an oil sourceneeds to not only contain unsaturated fatty acids, but specificallypolyunsaturated fatty acids in order to form the novel fattyacid-derived biomaterial described in this invention. Also, theresultant coating forms a cross-linked matrix that contains a very lowamount of residual aldehydes from the curing process that cannot bedetected unless harsh extraction conditions in an organic solvent areemployed.

Example 3: In-Vitro Hydration Ability of a Novel Biomaterial Derivedfrom Fish Oil

The following example characterizes the ability of the novel fattyacid-based hydrophobic cross-linked biomaterial to be hydrated andhydrolyzed, and to identify the chemical structure of the elutioncomponents released from the material from in-vitro and in-vivoexperiments.

Coated medical devices were cured in a high airflow oven at 200° F. for24 hours, after which the fish oil was converted into a fatty acidderived biomaterial coating encapsulating the polypropylene mesh byoxidation of the C═C bonds present in the fish oil resulting in theformation of oxidative byproducts (i.e., hydrocarbons, aldehydes,ketones, glycerides, fatty acids) while largely preserving the estersderived from the original oil triglycerides. Volatilization of thebyproducts followed by the formation of ester and lactone cross-linksresult in the solidification of oil into a bioabsorbable hydrophobiccross-linked biomaterial. FTIR and contact angle measurements wereperformed in order to determine the rate at which the fatty acid-derivedbiomaterial hydrated at 37° C. in 0.1 M PBS.

Contact angle measurements are taken by adding a drop of water to thesurface of a biomaterial in order to determine thehydrophobic/hydrophilic properties of the surface. The contact angle oneach side of the water droplet is measured in order to determine theability for the water droplet to spread (or “wet”) across the surface.High contact angles (>80 degrees) indicates a hydrophobic surface. Forexample PTFE, a hydrophobic material, typically presents contact anglemeasurements from 110-120 degrees. In contrast, low contact angles,indicate a hydrophilic surface (S. W. Jordan et al. Biomaterials. 2006,Vol. 27, pgs 3473-3481). Phospholipids, such as those found on theoutside surface of cellular membranes, have contact angles from 40-60degrees (S. W. Jordan et al, 2006).

FIG. 19 presents the contact angle measurements that were performed onthe fish oil derived biomaterial as a function of time. Initially,contact angles obtained from the fish fatty acid-derived biomaterialwere 100 degrees, which is indication a hydrophobic surface. However,less than 1 hour after exposure to the 0.1 M PBS solution the coatingrapidly hydrated and a contact angle of 60 degrees was obtained,indicating that a hydrophilic surface was produced. Physically, the fishfatty acid-derived biomaterial swelled and became slippery, but notsticky, and remained physically intact. After 6 hours of exposure to 0.1M PBS the coating contact angle plateaued at approximately 32 degrees.Physically the coating continued to exhibit a slippery, but not stickysurface and remain physically intact. The ability for the coating tohydrate and remain physically intact allows for improved handling andplacement during surgical implantation and minimizes frictional injuryto the patient, such as during a hernia repair or during a coronarystent implantation. Frictional injury caused by the placement of amedical device can lead to inflammation, which can result in clinicalcomplications such as adhesion formation in hernia repair and restenosisin coronary stent deployment.

FTIR analysis of the coating after 10 min of hydration in 0.1 M PBS ispresented in FIG. 20A. Excess water was removed prior to coatinganalysis and a Specac Silvergate ATR accessory with a Ge sensing crystalwas used for analysis of the coatings. The FTIR spectra in FIG. 20A showthat after being soaked in PBS solution for 10 min that the fattyacid-derived biomaterial rapidly absorbs water as indicated by thepresence of strong OH absorption bands after only 10 min of hydration.Additionally, FTIR measurements taken as a function of time out to 6hours and normalized to the carbonyl band height from the coating (FIG.20B) show that the OH bending absorption band continues to grow andlevels off at 4 hours as the coating hydrates, which is consistent withthe contact angle measurements. Finally, there is a shoulder on the OHbending mode at 1580 cm⁻¹, which is consistent with the ionization offatty acid COOH into COO⁻ in a hydrated environment (K. M. Faucher andR. A. Dluhy, Colloids and Surfaces A, 2003, Vol. 219, pgs 125-145).

Example 4: Analysis of In-Vitro Hydrolysis Chemistry of a NovelBiomaterial Derived from Fish Oil Using Basic Digestion

In the following example, coated medical devices were cured in a highairflow oven at 200° F. for 24 hours, after which the fish oil wasconverted into a cross-linked biomaterial gel coating encapsulating thepolypropylene mesh by oxidation of the C═C bonds present in the fish oilresulting in the formation of oxidative byproducts (i.e., hydrocarbons,aldehydes, ketones, glycerides, fatty acids) while largely preservingthe esters derived from the original oil triglycerides. Volatilizationof the byproducts followed by the formation of ester and lactonecross-links result in the solidification of oil into a bioabsorbablehydrophobic cross-linked biomaterial. The ability for the coating to behydrolyzed was investigated using basic digestion and the componentswere identified after neutralization using FTIR.

The fish fatty acid-derived biomaterial coating was immersed in 0.1 MNaOH solution and completely hydrolyzed in less than 20 min at roomtemperature with a clear, amber solution being produced. The basicsolution was then adjusted to neutral pH using HCl, after which aprecipitate formed. Both the neutralized solution and the precipitatewere analyzed using FTIR with a Specac Silvergate ATR accessory with aGe sensing crystal. The materials were allowed to dry on the Ge ATRcrystal prior to FTIR analysis. The FTIR spectra acquired of thehydrolyzed coating fractions are presented in FIG. 21. The FTIR spectrumof the neutralized solution after drying (FIG. 15A) shows OH, CH₂, esterC═O, fatty acid C═O and COO⁻ (antisymmetric and symmetric) absorptionbands. The OH and ester C═O are consistent with the presence of glyceroland glyceride components. The carboxylate ion (COO⁻) peaks from thehydrolysis solution are specific to the fatty acids in the coating asneither ketone nor aldehyde molecules exhibit absorption bands in thisarea (K. M. Faucher, 2003; Van de Voort et al., 1994). The strength ofthe OH and COO⁻ bands in FIG. 21A indicates that the hydrolysis solutionpredominantly contains fatty acids, glycerides, and glycerol components.FIG. 21B of the material that precipitated out upon neutralization ofthe basic digestion of the fatty acid-derived biomaterial coatingpresented a spectrum that is characteristic of fatty acidcrystallization spectra with the presence of strong CH₂, C═O, and CH₂scissoring, rocking, and wagging modes (K. M. Faucher, 2003). Theseresults are consistent with the GC-MS organic extraction of the coatingpresented in FIG. 14 (Example 1) that showed that the majority of thecoating components detected were fatty acids and glycerides.

Example 5: Analysis of In-Vitro Hydrolysis Chemistry of a NovelBiomaterial Derived from Fish Oil in 0.1 M PBS Solution

In the following example, coated medical devices (e.g., a polypropylenemesh) were cured in a high airflow oven at 200° F. for 24 hours, afterwhich the fish oil was converted into a cross-linked biomaterial gelcoating encapsulating the polypropylene mesh by oxidation of the C═Cbonds present in the fish oil resulting in the formation of oxidativebyproducts (i.e., hydrocarbons, aldehydes, ketones, glycerides, fattyacids) while largely preserving the esters derived from the original oiltriglycerides. Volatilization of the byproducts followed by theformation of ester and lactone cross-links result in the solidificationof oil into a bioabsorbable hydrophobic cross-linked biomaterial. Theability for the coating to be slowly hydrolyzed was investigated using0.1 M PBS solution. The PBS solution was analyzed using GC-FID fattyacid profile and GPC chromatographic measurements after hydrolysis ofthe fatty acid-derived biomaterial in PBS for 30 days.

FIG. 22 summarizes the fatty acid profile results obtained after dryingthe PBS solution and then performing a GC-FID fatty acid profileanalysis as described in the AOCS official method Ce 1-89b to identifythe fatty acids present in solution. FIG. 22 shows that the fatty acidsidentified from the PBS solution are the same as those detected from thecoating itself (FIG. 22 versus FIG. 13). GPC analysis was also conductedon the hydrolysis solution and the results are summarized in Table 5.The GPC results showed that the vast majority of molecular weightcomponents identified (80%) were below a molecular weight of 500, whichis consistent with the fatty acid components of the coating. Also,glyceride components of the coating could be identified with molecularweights around 1000 (15% of the coating). The GPC results also showed anegligible amount (approximately 4%) of high molecular weight gel. TheGPC results support the other analytical characterization experiments onthe fatty acid-derived coatings which show that the fatty acid-derivedbiomaterial is comprised of cross-linked glycerides and fatty acids, andthat the coating is non-polymeric.

TABLE 5 GPC Analysis of PBS Hydrolysis Solution after Contact with FishFatty acid-Derived Biomaterial for 30 days. Molecular Weight % Peak AreaPotential Identity >110,000 4 High Molecular Weight Gel >1000 1Partially Hydrolyzed Gel 1000 15 Glycerides <500 80 Fatty Acids

Example 6: FTIR Analysis of Fish Fatty Acid-Derived Biomaterials atVarious Time Points after being Implanted In-Vivo

In the following example, coated medical devices (e.g., a polypropylenemesh) were cured in a high airflow oven at 200° F. for 24 hours, afterwhich the fish oil was converted into a cross-linked biomaterial gelcoating encapsulating the polypropylene mesh by oxidation of the C═Cbonds present in the fish oil resulting in the formation of oxidativebyproducts (i.e., hydrocarbons, aldehydes, ketones, glycerides, fattyacids) while largely preserving the esters derived from the original oiltriglycerides. Volatilization of the byproducts followed by theformation of ester and lactone cross-links result in the solidificationof oil into a bioabsorbable hydrophobic cross-linked biomaterial. Thisexample was performed to assess the coating described herein afterimplantation in a rat abdominal wall defect for various lengths of time.Mesh samples were implanted in a rat abdominal wall defect for 4, 7, 14,21, and 28 days. At each time point, the entire piece of mesh and somesurrounding tissue was explanted, wrapped in saline soaked gauze andplaced in specimen containers. Sections of the explanted mesh (approx. 1cm×1 cm) were dissected, soaked in NERL water overnight in arefrigerator and air dried in a hood overnight. The dried mesh explantswere analyzed using a Specac Silvergate HATR Ge accessory to analyzebulk sections of the coating.

Physically, the explants were observed to have increased tissuein-growth on the rough side (peritoneal side) over time. This in-growthwas very difficult to remove at the later time points (21 and 28 days).A very thin layer of tissue was noted over the smooth side of theexplants at the later time points (21 and 28 days). This layer of tissuewas not attached to the coating, but was lying on top of it and waseasily removed. In addition, the coating appeared to be absorbed overthe course of the example as indicated by a visible thinning of thecoating where bare polypropylene fibers were exposed where they arenormally buried on the continuous smooth side of the coating prior toimplantation.

FIG. 23 shows the plot of the normalized changes in lactone/estercross-linking (♦), glyceride ester (▪), fatty acid (▴), and protein (X)band peak height normalized to the CH₂ antisymmetric stretch as afunction of time. This data numerically summarizes the changes in peakheight observed in the FTIR data. These results show that the meshcoating is being hydrolyzed and absorbed in vivo. Chemically, it appearsthat it is occurring by the absorption of the short chain fatty acid,ketone, and aldehyde byproducts in addition to the breaking down thealiphatic peroxide, anhydride, and lactone cross-linking bands. Fromliterature studies on the metabolism of triglycerides and fatty acids inthe GI tract in vivo, we would expect the shorter chain lengthbyproducts to be absorbed more quickly than the cross-linked glyceridecomponents. The FTIR data appears to be consistent with this result.Without being bound by any particular theory, based on the hydrolysis ofthe cross-linking bands and prior literature, the FTIR data supports ahydrolysis and/or enzymatic (i.e., lipase) bioabsorption of the coating.

Example 7: GC-FID Fatty Acid Profile Analysis of Fish Fatty Acid-DerivedBiomaterials at Various Time Points after being Implanted In-Vivo

In this example, coated medical devices were cured in a high airflowoven at 200° F. for 24 hours, after which the fish oil was convertedinto a cross-linked biomaterial gel coating encapsulating thepolypropylene mesh by oxidation of the C═C bonds present in the fish oilresulting in the formation of oxidative byproducts (i.e., hydrocarbons,aldehydes, ketones, glycerides, fatty acids) while largely preservingthe esters derived from the original oil triglycerides. Volatilizationof the byproducts followed by the formation of ester and lactonecross-links result in the solidification of oil into a bioabsorbablehydrophobic cross-linked biomaterial. This example was performed toassess the coating described herein after implantation in a ratabdominal wall defect for various lengths of time. Mesh samples wereimplanted in a rat abdominal wall defect for 4, 7, 14, and 21 days. Ateach time point, the entire piece of mesh and some surrounding tissuewas explanted, placed in specimen containers and frozen at −80° C. untilanalysis. Sections of the explanted mesh (approx. 2.5 cm×2.5 cm) weredissected from tissue and subjected to GC-FID fatty acid profileanalysis using AOCS method Ce 1-89b.

Similar to the FTIR analysis described in Example 4, the explants wereobserved to have increased tissue in-growth on the rough side(peritoneal side) over time. This in-growth was very difficult to removeat the later time points (21 days). A very thin layer of tissue wasnoted over the smooth side of the explants at the later time points andthere was tissue in-growth through the polypropylene mesh (at 21 days).In addition, the coating appeared to be absorbed over the course of theexample as indicated by a visible thinning of the coating.

FIG. 24 presents the GC-FID fatty acid profile analysis of the explantedfish-oil derived coatings at various time points and normalized with aninternal standard. This data shows that the fatty acids are beingabsorbed away as the tissue is growing into the coating. The significantdrop in fatty acid composition at day 21 correlates with visible tissuein-growth and these findings are consistent with a bioabsorptionmechanism of the coating.

Example 8: Biocompatibility Testing of Fatty Acid-Derived HydrophobicBiomaterials

In this example, coated medical devices were cured in a high airflowoven at 200° F. for 24 hours, after which the fish oil was convertedinto a cross-linked biomaterial gel coating encapsulating thepolypropylene mesh by oxidation of the C═C bonds present in the fish oilresulting in the formation of oxidative byproducts (i.e. hydrocarbons,aldehydes, ketones, glycerides, fatty acids) while largely preservingthe esters derived from the original oil triglycerides. Volatilizationof the byproducts followed by the formation of ester and lactonecross-links result in the solidification of oil into a bioabsorbablehydrophobic cross-linked biomaterial. This example was performed toassess the biocompatibility and in-vivo performance of the fish fattyacid-derived coating.

The fish-oil derived coating described herein was subjected to ISO 10993(Biological Evaluation of Medical Device) Testing. The results aresummarized in Table 6. Based on the results in Table 6, the novel fishfatty acid-derived biomaterial was demonstrated to be biocompatible. Thefish fatty acid-derived biomaterial coating was implanted in a ratabdominal defect model to determine the ability for the coating toreduce adhesion formation in comparison to a polypropylene control. Thesamples were explanted at 4, 7, 14, 21, and 28 days and given anadhesion score, 0—no adhesions; 1—adhesions freed by gentle bluntdissection; 2—adhesions freed by aggressive blunt dissection;3—Adhesions requiring sharp dissection (cutting). The results (Table 7)showed that the fish-oil derived biomaterial reduced the incidence andtenacity of the adhesions in addition when compared to the polypropylenemesh control.

TABLE 6 Summary of ISO 10993 Biological Evaluation of Medical DeviceTesting Results Test Result Sensitization Test Passed GenotoxicityNon-Mutagenic Irritation Passed Cytotoxicity Non-cytotoxic PyrogenicityNon-pyrogenic Acute System Toxicity Non-Toxic Wound Healing Rate NormalChronic Toxicity (13 and 26 Passed weeks)

TABLE 7 Summary of Rat Abdominal Defect Study Fish Oil Derived BarePolypropylene Biomaterial Control (Mean Adhesion (Mean Adhesion DaysImplanted Score) Score)  4 day 0.4 1  7 day 1.4 2.7 14 day 1.6 2.3 21day 1.5 2.8 28 day 1.2 2.7

Example 9: In Vivo Performance of Fish Fatty Acid Derived Biomaterial

The coating prepared as described in Example 7 was implanted in a ratabdominal wall defect model for 30 days to assess the inflammatoryresponse of the coating, as well as its ability to reduce adhesionformation as compared to a bare polypropylene mesh. Histopathology wasconducted on the explanted samples using standard H&E staining todetermine the amount of inflammation present on the coated samples andthe bare polypropylene samples. The results are shown in Table 8, below.Histopathology on the coated samples revealed minimal inflammationassociated with the coating itself, as most inflammatory cells presentwere associated with the polypropylene monofilaments. Histology alsoconfirmed what was seen in the gross adhesion assessment; minimal to notissue attachment on the visceral surface of the implants. At the 30-daytime point, both the bare polypropylene and the coated samplesdemonstrated good tissue incorporation on the abdominal wall surface ofthe implants.

TABLE 8 Inflammation Scores, 30-Day Rat Implant Study Inflammation ScoreAdhesion Score Test Group (mean score) (mean score) Bare Polypropylene3.1 2.5 Fish Oil Derived Biomaterial 2.0 1.2

[Inflammation Scale: 1—no inflammatory cells present; 2—mild, fewinflammatory cells present; 3—moderate; 4—severe, intense inflammatoryresponse] [Adhesion Scale: 0—No Adhesions; 1—Adhesions freed by gentleblunt dissection; 2—Adhesions freed by aggressive blunt dissection;3—Adhesions requiring sharp dissection (cutting)]

Example 10: Ability to Form Fatty Acid-Derived Biomaterials withDifferent Physical Properties and Chemistries by Altering FormationProcess

In this example, different fish fatty acid-based biomaterial deviceswere produced. First, a partially cured fish oil gel was produced bytaking 1 L of fish oil and curing it in a jacketed glass reactor whilebubbling oxygen through it at 200° F. for 20 hours with a finalviscosity range of 120 k-130 k cps. The stand-alone film was createdusing the partially cured fish oil, casting it onto a PTFE linedstainless steel pan, and initially setting the coating by UV lampexposure using germicidal lamps for 25 min (i.e., photo-oxidation) andthen subjecting the film to a final heat curing process at 24 hours at200° F. Fish oil coated mesh samples were created by coating a piece ofbare mesh in pure fish oil and curing using either 150° F. (72 hours) or200° F. (24 hours) curing conditions. In this example, the effect ofcuring process on the composition of fish-oil derived biomaterialcoatings was studied.

FTIR analysis of the different cured materials (i.e., 150° F. coating,200° F. coating, film, and partially cured fish oil) is summarized inFIG. 25. The data in FIG. 25 shows that altering curing conditionsproduces materials with differing amounts of fatty acid byproducts,lactone/ester cross-linking, and cis-trans C═C isomer ratios. Thesedifferences are also reflected in the GC-FID fatty acid profilesobtained using the official AOCS Ce 1-89b, (FIG. 26), which shows thatby altering the curing process the final fatty acid composition can bealtered. The alteration of fatty acid composition can affect both drugdelivery release profile and potentially the inflammatory properties ofthe fatty acid-derived biomaterial.

Example 11: Tailoring Drug Release Profile of Coating

The following examples demonstrate the ability to alter the chemistryand position of the drug-containing layer in cured fish oil meshcoatings. The chemistry of the various coating layers can be adjusted byemploying different curing conditions and/or vitamin E composition.

The Effects of Curing Time and Temperature

All coated mesh samples were 1×1″ and dissolution was performed in 0.01M PBS solution. Drug release coated mesh samples were created by mixingthe fish oil and drug followed by coating a piece of bare mesh andcuring using either 150° F. (72 hours) or 200° F. (24 hours) curingconditions.

FIG. 27 depicts the drug release profile measured for ananti-inflammatory drug. The figure compares two curing conditions,heating for 24 hours at 200° F. or heating for 3 days at 150° F. Thestarting material comprised 3.29% model anti-inflammatory drug (afternMP solvent was removed) in fish oil (EPAX 3000 TG).

These results show that adjusting curing temperature can alter therelease of an anti-inflammatory therapeutic agent. The sample cured at150° F. (▴), due to the lower amount of cross-linking and final fattyacid composition, releases more rapidly than the more cross-linked 200°F. sample (♦). This illustrates the flexibility of the coating systemwhere the release rate of the therapeutic can be altered based on thechemistry of the fatty acid-derived biomaterial coating chemistry, whichcan be tailored based on the cure time, type of oil utilized, curemethods, thickness of coating, and/or temperature conditions employed.

FIG. 28 depicts a further drug release profile measured for ananti-proliferative. The figure compares two curing conditions, heatingfor 24 hours at 200° F. or heating for 3 days at 150° F. The startingmaterial comprised 2.84% Compound E in fish oil (EPAX 3000 TG). Nosolvent was used as Compound E was soluble in the fish oil with slightheating at 37° C. The initial drug loading after curing, based on HPLCmeasurements, was about 478 μg (14.22% recovery, ♦) in the 200° F. curedcoating and about 1158 μg (26.00% recovery, ▴) in the 150° F. curedcoating. It is to be noted that the percentage amount recovered isdependent on the coating weight and amount of drug detected using HPLCmethods after drug extraction from the cured fish oil coating.

These results show that adjusting curing temperature and drug layercoating position can also alter the release of Compound E, ananti-proliferative. The 150° F. samples, due to the lower amount ofcross-linking, release more rapidly than the more cross-linked samplescured at 200° F. Finally, the drug extraction results show that theCompound E, which is a peptide, is more stable using the 150° F. curingconditions (i.e. higher HPLC assay recovery).

In Combination with Vitamin E

All coated mesh samples were 1×1″ and dissolution was performed in 0.01M PBS solution. All drug samples were loaded as a cured first layer onthe mesh and were created by mixing the liquid fish oil and drugtogether, with or without solvent, followed by coating a piece of baremesh and curing at 150° F. for 3 days.

FIG. 29 shows the effects of vitamin E composition on the cross-linkingand trans C═C band as a function of temperature. As the amount ofVitamin E is increased the amount of lactone/ester cross-linking isreduced and the amount of oxidation (as monitored by the trans C═C band)is also reduced. FIG. 30 depicts the drug release profile measured forCompound D. The figure compares varying amounts of vitamin E added tothe starting material prior to curing for 3 days at 150° F. The startingmaterials comprised 4.88% Compound D (after solvent removal) in varyingamounts of vitamin E in fish oil coatings (0-5%). The initial drugloading for the 100% fish oil sample (no vitamin E) was after curing,based on HPLC measurements, was about 270 μg (5.5% recovery, •) in theoverlayer, and about 378 μg (16.5% recovery, ▴) in the first coating(underlayer). The initial drug loading for the 5% vitamin E in fish oilsample was after curing, based on HPLC measurements, was about 3584 μg(66.7% recovery, +) in the overlayer, and about 3013 μg (52.2% recovery,▪) in the first coating (underlayer).

These results show that altering the vitamin E composition can alter therelease of a therapeutic from the cured fish oil coating. Increasing theamount of vitamin E results in lengthening and slowing the release ofCompound D into the dissolution buffer, due to its enhanced solubilityand affinity for the vitamin E component in the cured fish oil coating.Additionally, the cured 5% vitamin E/fish oil overlayer coating resultsin an increase in the amount of drug released when compared to theencapsulated mesh.

Example 12: Cured Oil Coatings Loaded with Therapeutics and Applied toMetallic Stents

In this particular embodiment, the application of cured oil coatingsloaded with a therapeutic and applied to a cardiac stent are presented.The flow diagram presenting the process to create a cured coating on astent loaded with a therapeutic is outlined in FIG. 31. Briefly, apartially cured fish oil coating is created in a reaction vessel underagitation with heating at 200° F. for 20 hours. The fatty acid-derivedcoating is mixed with the therapeutic of interest, and vitamin E with asolvent and then sprayed onto the stent to create a coating. The coatingis annealed to the stent surface by heating at 200° F. for 7 hours tocreate a uniform coating. A coating with a model anti-inflammatory agentshowed that this process allowed for 90% of the drug to be recoveredafter curing as determined using extraction of the drug from the devicewith HPLC analysis. FIG. 32 shows the drug release profile for thiscoating in 0.01 M PBS buffer going out to 20 days with over a 90%recovery of the drug recovered using this process.

Numerous modifications and alternative embodiments of the presentinvention will be apparent to those skilled in the art in view of theforegoing description. Accordingly, this description is to be construedas illustrative only and is for the purpose of teaching those skilled inthe art the best mode for carrying out the present invention. Details ofthe structure may vary substantially without departing from the spiritof the invention, and exclusive use of all modifications that comewithin the scope of the appended claims is reserved. It is intended thatthe present invention be limited only to the extent required by theappended claims and the applicable rules of law.

All literature and similar material cited in this application,including, patents, patent applications, articles, books, treatises,dissertations and web pages, regardless of the format of such literatureand similar materials, are expressly incorporated by reference in theirentirety. In the event that one or more of the incorporated literatureand similar materials differs from or contradicts this application,including defined terms, term usage, described techniques, or the like,this application controls.

The section headings used herein are for organizational purposes onlyand are not to be construed as limiting the subject matter described inany way.

While the present invention has been described in conjunction withvarious embodiments and examples, it is not intended that the presentteachings be limited to such embodiments or examples. On the contrary,the present invention encompasses various alternatives, modifications,and equivalents, as will be appreciated by those of skill in the art.

The claims should not be read as limited to the described order orelements unless stated to that effect. It should be understood thatvarious changes in form and detail may be made without departing fromthe scope of the appended claims. Therefore, all embodiments that comewithin the scope and spirit of the following claims and equivalentsthereto are claimed.

1-20. (canceled)
 21. A cured biomaterial comprising: fatty acidscross-linked to each other via cross-linking bridges, wherein the fattyacids are derived from fish oil; wherein the cured biomaterial ishydrolysable in vivo and a composition of the fatty acids before curingcomprises at least about twenty-five percent saturated fatty acids andat least about thirty percent polyunsaturated fatty acids in terms ofarea % by gas chromatography fatty acid profile.
 22. The curedbiomaterial of claim 21, wherein the fatty acids comprise approximately5-50% C₁₆ fatty acids in terms of area % by gas chromatography fattyacid profile.
 23. A medical device having a coating formed by the curedbiomaterial of claim
 21. 24. The cured biomaterial of claim 21, whereinthe fatty acids are cross-linked to each other by ester and lactonebonds.
 25. The cured biomaterial of claim 21, wherein thepolyunsaturated fatty acids are primarily C₂₀ fatty acids or longer. 26.The cured biomaterial of claim 21, wherein the polyunsaturated fattyacids are primarily C_(20:5) and C_(22:6) fatty acids.
 27. The curedbiomaterial of claim 21, wherein the cross-linking bridges include acombination of peroxide bridges, ether bridges, and hydrocarbon bridges.28. A cured biomaterial comprising: fatty acids cross-linked to eachother via cross-linking bridges, wherein the fatty acids are derivedfrom fish oil; wherein the cured biomaterial is hydrolysable in vivo anda composition of the fatty acids before curing comprises at least fivedifferent fatty acid species of at least five percent each in terms ofarea % by gas chromatography fatty acid profile.
 29. The curedbiomaterial of claim 28, wherein the fatty acids comprise approximately5-50% C₁₆ fatty acids in terms of area % by gas chromatography fattyacid profile.
 30. A medical device having a coating formed by thebiomaterial of claim
 28. 31. The cured biomaterial of claim 28, whereinthe fatty acids are cross-linked to each other by ester and lactonebonds.
 32. The cured biomaterial of claim 28, wherein the at least fivedifferent fatty acids include any combination of C_(14:0), C_(16:0),C_(16:1), C_(18:1), C_(18:2), C_(20:5), and C_(22:6) fatty acids. 33.The cured biomaterial of claim 28, wherein the cross-linking bridgesinclude a combination of peroxide bridges, ether bridges, andhydrocarbon bridges.